vulkan: Implement blend modes

This is another example for a 2-texture shader.
So far, only separable blend modes are implemented.
The implementation is not optimized, with an
if-else cascade in the shader.

17 files changed, 515 insertions, 1 deletions

diff --git a/gsk/gskvulkanblendmodepipeline.c b/gsk/gskvulkanblendmodepipeline.c
new file mode 100644
index 0000000000..062921e0b2
--- /dev/null
+++ b/gsk/gskvulkanblendmodepipeline.c
@@ -0,0 +1,146 @@
+#include "config.h"
+
+#include "gskvulkanblendmodepipelineprivate.h"
+
+struct _GskVulkanBlendModePipeline
+{
+  GObject parent_instance;
+};
+
+typedef struct _GskVulkanBlendModeInstance GskVulkanBlendModeInstance;
+
+struct _GskVulkanBlendModeInstance
+{
+  float rect[4];
+  float start_tex_rect[4];
+  float end_tex_rect[4];
+  guint32 blend_mode;
+};
+
+G_DEFINE_TYPE (GskVulkanBlendModePipeline, gsk_vulkan_blend_mode_pipeline, GSK_TYPE_VULKAN_PIPELINE)
+
+static const VkPipelineVertexInputStateCreateInfo *
+gsk_vulkan_blend_mode_pipeline_get_input_state_create_info (GskVulkanPipeline *self)
+{
+  static const VkVertexInputBindingDescription vertexBindingDescriptions[] = {
+      {
+          .binding = 0,
+          .stride = sizeof (GskVulkanBlendModeInstance),
+          .inputRate = VK_VERTEX_INPUT_RATE_INSTANCE
+      }
+  };
+  static const VkVertexInputAttributeDescription vertexInputAttributeDescription[] = {
+      {
+          .location = 0,
+          .binding = 0,
+          .format = VK_FORMAT_R32G32B32A32_SFLOAT,
+          .offset = 0,
+      },
+      {
+          .location = 1,
+          .binding = 0,
+          .format = VK_FORMAT_R32G32B32A32_SFLOAT,
+          .offset = G_STRUCT_OFFSET (GskVulkanBlendModeInstance, start_tex_rect),
+      },
+      {
+          .location = 2,
+          .binding = 0,
+          .format = VK_FORMAT_R32G32B32A32_SFLOAT,
+          .offset = G_STRUCT_OFFSET (GskVulkanBlendModeInstance, end_tex_rect),
+      },
+      {
+          .location = 3,
+          .binding = 0,
+          .format = VK_FORMAT_R32_UINT,
+          .offset = G_STRUCT_OFFSET (GskVulkanBlendModeInstance, blend_mode),
+      }
+  };
+  static const VkPipelineVertexInputStateCreateInfo info = {
+      .sType = VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_STATE_CREATE_INFO,
+      .vertexBindingDescriptionCount = G_N_ELEMENTS (vertexBindingDescriptions),
+      .pVertexBindingDescriptions = vertexBindingDescriptions,
+      .vertexAttributeDescriptionCount = G_N_ELEMENTS (vertexInputAttributeDescription),
+      .pVertexAttributeDescriptions = vertexInputAttributeDescription
+  };
+
+  return &info;
+}
+
+static void
+gsk_vulkan_blend_mode_pipeline_finalize (GObject *gobject)
+{
+  //GskVulkanBlendModePipeline *self = GSK_VULKAN_BLUR_PIPELINE (gobject);
+
+  G_OBJECT_CLASS (gsk_vulkan_blend_mode_pipeline_parent_class)->finalize (gobject);
+}
+
+static void
+gsk_vulkan_blend_mode_pipeline_class_init (GskVulkanBlendModePipelineClass *klass)
+{
+  GskVulkanPipelineClass *pipeline_class = GSK_VULKAN_PIPELINE_CLASS (klass);
+
+  G_OBJECT_CLASS (klass)->finalize = gsk_vulkan_blend_mode_pipeline_finalize;
+
+  pipeline_class->get_input_state_create_info = gsk_vulkan_blend_mode_pipeline_get_input_state_create_info;
+}
+
+static void
+gsk_vulkan_blend_mode_pipeline_init (GskVulkanBlendModePipeline *self)
+{
+}
+
+GskVulkanPipeline *
+gsk_vulkan_blend_mode_pipeline_new (GdkVulkanContext        *context,
+                                    VkPipelineLayout         layout,
+                                    const char              *shader_name,
+                                    VkRenderPass             render_pass)
+{
+  return gsk_vulkan_pipeline_new (GSK_TYPE_VULKAN_BLEND_MODE_PIPELINE, context, layout, shader_name, render_pass);
+}
+
+gsize
+gsk_vulkan_blend_mode_pipeline_count_vertex_data (GskVulkanBlendModePipeline *pipeline)
+{
+  return sizeof (GskVulkanBlendModeInstance);
+}
+
+void
+gsk_vulkan_blend_mode_pipeline_collect_vertex_data (GskVulkanBlendModePipeline *pipeline,
+                                                    guchar                *data,
+                                                    const graphene_rect_t *bounds,
+                                                    const graphene_rect_t *start_bounds,
+                                                    const graphene_rect_t *end_bounds,
+                                                    GskBlendMode blend_mode)
+{
+  GskVulkanBlendModeInstance *instance = (GskVulkanBlendModeInstance *) data;
+
+  instance->rect[0] = bounds->origin.x;
+  instance->rect[1] = bounds->origin.y;
+  instance->rect[2] = bounds->size.width;
+  instance->rect[3] = bounds->size.height;
+
+  instance->start_tex_rect[0] = (bounds->origin.x - start_bounds->origin.x)/start_bounds->size.width;
+  instance->start_tex_rect[1] = (bounds->origin.y - start_bounds->origin.y)/start_bounds->size.height;
+  instance->start_tex_rect[2] = (bounds->size.width + bounds->origin.x - start_bounds->origin.x)/start_bounds->size.width;
+  instance->start_tex_rect[3] = (bounds->size.height + bounds->origin.y - start_bounds->origin.y)/start_bounds->size.height;
+
+  instance->end_tex_rect[0] = (bounds->origin.x - end_bounds->origin.x)/end_bounds->size.width;
+  instance->end_tex_rect[1] = (bounds->origin.y - end_bounds->origin.y)/end_bounds->size.height;
+  instance->end_tex_rect[2] = (bounds->size.width + bounds->origin.x - end_bounds->origin.x)/end_bounds->size.width;
+  instance->end_tex_rect[3] = (bounds->size.height + bounds->origin.y - end_bounds->origin.y)/end_bounds->size.height;
+
+  instance->blend_mode = blend_mode;
+}
+
+gsize
+gsk_vulkan_blend_mode_pipeline_draw (GskVulkanBlendModePipeline *pipeline,
+                                     VkCommandBuffer        command_buffer,
+                                     gsize                  offset,
+                                     gsize                  n_commands)
+{
+  vkCmdDraw (command_buffer,
+             6, n_commands,
+             0, offset);
+
+  return n_commands;
+}
diff --git a/gsk/gskvulkanblendmodepipelineprivate.h b/gsk/gskvulkanblendmodepipelineprivate.h
new file mode 100644
index 0000000000..67822e4f9b
--- /dev/null
+++ b/gsk/gskvulkanblendmodepipelineprivate.h
@@ -0,0 +1,37 @@
+#ifndef __GSK_VULKAN_BLEND_MODE_PIPELINE_PRIVATE_H__
+#define __GSK_VULKAN_BLEND_MODE_PIPELINE_PRIVATE_H__
+
+#include <graphene.h>
+
+#include "gskvulkanpipelineprivate.h"
+#include "gskenums.h"
+
+G_BEGIN_DECLS
+
+typedef struct _GskVulkanBlendModePipelineLayout GskVulkanBlendModePipelineLayout;
+
+#define GSK_TYPE_VULKAN_BLEND_MODE_PIPELINE (gsk_vulkan_blend_mode_pipeline_get_type ())
+
+G_DECLARE_FINAL_TYPE (GskVulkanBlendModePipeline, gsk_vulkan_blend_mode_pipeline, GSK, VULKAN_BLEND_MODE_PIPELINE, GskVulkanPipeline)
+
+GskVulkanPipeline * gsk_vulkan_blend_mode_pipeline_new                 (GdkVulkanContext           *context,
+                                                                        VkPipelineLayout            layout,
+                                                                        const char                 *shader_name,
+                                                                        VkRenderPass                render_pass);
+
+gsize               gsk_vulkan_blend_mode_pipeline_count_vertex_data   (GskVulkanBlendModePipeline *pipeline);
+void                gsk_vulkan_blend_mode_pipeline_collect_vertex_data (GskVulkanBlendModePipeline *pipeline,
+                                                                        guchar                     *data,
+                                                                        const graphene_rect_t      *bounds,
+                                                                        const graphene_rect_t      *start_bounds,
+                                                                        const graphene_rect_t      *end_bounds,
+                                                                        GskBlendMode                blend_mode);
+gsize               gsk_vulkan_blend_mode_pipeline_draw                (GskVulkanBlendModePipeline *pipeline,
+                                                                        VkCommandBuffer             command_buffer,
+                                                                        gsize                       offset,
+                                                                        gsize                       n_commands);
+
+
+G_END_DECLS
+
+#endif /* __GSK_VULKAN_BLEND_MODE_PIPELINE_PRIVATE_H__ */
diff --git a/gsk/gskvulkanrender.c b/gsk/gskvulkanrender.c
index 06b622db59..007f3d4ac2 100644
--- a/gsk/gskvulkanrender.c
+++ b/gsk/gskvulkanrender.c
@@ -10,6 +10,7 @@
 #include "gskvulkanpipelineprivate.h"
 #include "gskvulkanrenderpassprivate.h"
 
+#include "gskvulkanblendmodepipelineprivate.h"
 #include "gskvulkanblendpipelineprivate.h"
 #include "gskvulkanblurpipelineprivate.h"
 #include "gskvulkanborderpipelineprivate.h"
@@ -392,6 +393,9 @@ gsk_vulkan_render_get_pipeline (GskVulkanRender       *self,
     { "crossfade",                  2, gsk_vulkan_cross_fade_pipeline_new },
     { "crossfade-clip",             2, gsk_vulkan_cross_fade_pipeline_new },
     { "crossfade-clip-rounded",     2, gsk_vulkan_cross_fade_pipeline_new },
+    { "blendmode",                  2, gsk_vulkan_blend_mode_pipeline_new },
+    { "blendmode-clip",             2, gsk_vulkan_blend_mode_pipeline_new },
+    { "blendmode-clip-rounded",     2, gsk_vulkan_blend_mode_pipeline_new },
   };
 
   g_return_val_if_fail (type < GSK_VULKAN_N_PIPELINES, NULL);
diff --git a/gsk/gskvulkanrenderpass.c b/gsk/gskvulkanrenderpass.c
index 866a4eaa73..3f9c7aa0c6 100644
--- a/gsk/gskvulkanrenderpass.c
+++ b/gsk/gskvulkanrenderpass.c
@@ -6,6 +6,7 @@
 #include "gskrendernodeprivate.h"
 #include "gskrenderer.h"
 #include "gskroundedrectprivate.h"
+#include "gskvulkanblendmodepipelineprivate.h"
 #include "gskvulkanblendpipelineprivate.h"
 #include "gskvulkanblurpipelineprivate.h"
 #include "gskvulkanborderpipelineprivate.h"
@@ -50,6 +51,7 @@ typedef enum {
   GSK_VULKAN_OP_COLOR_TEXT,
   /* GskVulkanOpCrossFade */
   GSK_VULKAN_OP_CROSS_FADE,
+  GSK_VULKAN_OP_BLEND_MODE,
   /* GskVulkanOpPushConstants */
   GSK_VULKAN_OP_PUSH_VERTEX_CONSTANTS,
 } GskVulkanOpType;
@@ -180,10 +182,28 @@ gsk_vulkan_render_pass_add_node (GskVulkanRenderPass           *self,
       return;
     case GSK_REPEAT_NODE:
     case GSK_SHADOW_NODE:
-    case GSK_BLEND_NODE:
     default:
       FALLBACK ("Unsupported node '%s'\n", node->node_class->type_name);
 
+    case GSK_BLEND_NODE:
+      if (gsk_blend_node_get_blend_mode (node) == GSK_BLEND_MODE_COLOR ||
+          gsk_blend_node_get_blend_mode (node) == GSK_BLEND_MODE_HUE ||
+          gsk_blend_node_get_blend_mode (node) == GSK_BLEND_MODE_SATURATION ||
+          gsk_blend_node_get_blend_mode (node) == GSK_BLEND_MODE_LUMINOSITY)
+        FALLBACK ("Nonseparable blend modes not implemented\n");
+      if (gsk_vulkan_clip_contains_rect (&constants->clip, &node->bounds))
+        pipeline_type = GSK_VULKAN_PIPELINE_BLEND_MODE;
+      else if (constants->clip.type == GSK_VULKAN_CLIP_RECT)
+        pipeline_type = GSK_VULKAN_PIPELINE_BLEND_MODE_CLIP;
+      else if (constants->clip.type == GSK_VULKAN_CLIP_ROUNDED_CIRCULAR)
+        pipeline_type = GSK_VULKAN_PIPELINE_BLEND_MODE_CLIP_ROUNDED;
+      else
+        FALLBACK ("Blend nodes can't deal with clip type %u\n", constants->clip.type);
+      op.type = GSK_VULKAN_OP_BLEND_MODE;
+      op.render.pipeline = gsk_vulkan_render_get_pipeline (render, pipeline_type);
+      g_array_append_val (self->render_ops, op);
+       return;
+
     case GSK_CROSS_FADE_NODE:
       if (gsk_vulkan_clip_contains_rect (&constants->clip, &node->bounds))
         pipeline_type = GSK_VULKAN_PIPELINE_CROSS_FADE;
@@ -758,6 +778,24 @@ gsk_vulkan_render_pass_upload (GskVulkanRenderPass  *self,
           }
           break;
 
+        case GSK_VULKAN_OP_BLEND_MODE:
+          {
+            GskRenderNode *top = gsk_blend_node_get_top_child (op->crossfade.node);
+            GskRenderNode *bottom = gsk_blend_node_get_bottom_child (op->crossfade.node);
+
+            op->crossfade.start = gsk_vulkan_render_pass_get_node_as_texture (self,
+                                                                              render,
+                                                                              uploader,
+                                                                              top,
+                                                                              &top->bounds);
+            op->crossfade.end = gsk_vulkan_render_pass_get_node_as_texture (self,
+                                                                            render,
+                                                                            uploader,
+                                                                            bottom,
+                                                                            &bottom->bounds);
+          }
+          break;
+
         default:
           g_assert_not_reached ();
         case GSK_VULKAN_OP_COLOR:
@@ -843,6 +881,11 @@ gsk_vulkan_render_pass_count_vertex_data (GskVulkanRenderPass *self)
           n_bytes += op->crossfade.vertex_count;
           break;
 
+        case GSK_VULKAN_OP_BLEND_MODE:
+          op->crossfade.vertex_count = gsk_vulkan_blend_mode_pipeline_count_vertex_data (GSK_VULKAN_BLEND_MODE_PIPELINE (op->crossfade.pipeline));
+          n_bytes += op->crossfade.vertex_count;
+          break;
+
         default:
           g_assert_not_reached ();
         case GSK_VULKAN_OP_PUSH_VERTEX_CONSTANTS:
@@ -1049,6 +1092,22 @@ gsk_vulkan_render_pass_collect_vertex_data (GskVulkanRenderPass *self,
           }
           break;
 
+        case GSK_VULKAN_OP_BLEND_MODE:
+          {
+            GskRenderNode *top = gsk_blend_node_get_top_child (op->crossfade.node);
+            GskRenderNode *bottom = gsk_blend_node_get_bottom_child (op->crossfade.node);
+
+            op->crossfade.vertex_offset = offset + n_bytes;
+            gsk_vulkan_blend_mode_pipeline_collect_vertex_data (GSK_VULKAN_BLEND_MODE_PIPELINE (op->crossfade.pipeline),
+                                                                data + n_bytes + offset,
+                                                                &op->crossfade.node->bounds,
+                                                                &top->bounds,
+                                                                &bottom->bounds,
+                                                                gsk_blend_node_get_blend_mode (op->crossfade.node));
+            n_bytes += op->crossfade.vertex_count;
+          }
+          break;
+
         default:
           g_assert_not_reached ();
         case GSK_VULKAN_OP_PUSH_VERTEX_CONSTANTS:
@@ -1091,6 +1150,7 @@ gsk_vulkan_render_pass_reserve_descriptor_sets (GskVulkanRenderPass *self,
           break;
 
         case GSK_VULKAN_OP_CROSS_FADE:
+        case GSK_VULKAN_OP_BLEND_MODE:
           op->crossfade.descriptor_set_start = gsk_vulkan_render_reserve_descriptor_set (render, op->crossfade.start);
           op->crossfade.descriptor_set_end = gsk_vulkan_render_reserve_descriptor_set (render, op->crossfade.end);
           break;
@@ -1432,6 +1492,40 @@ gsk_vulkan_render_pass_draw (GskVulkanRenderPass     *self,
                                                                      current_draw_index, 1);
           break;
 
+        case GSK_VULKAN_OP_BLEND_MODE:
+          if (current_pipeline != op->crossfade.pipeline)
+            {
+              current_pipeline = op->crossfade.pipeline;
+              vkCmdBindPipeline (command_buffer,
+                                 VK_PIPELINE_BIND_POINT_GRAPHICS,
+                                 gsk_vulkan_pipeline_get_pipeline (current_pipeline));
+              vkCmdBindVertexBuffers (command_buffer,
+                                      0,
+                                      1,
+                                      (VkBuffer[1]) {
+                                          gsk_vulkan_buffer_get_buffer (vertex_buffer)
+                                      },
+                                      (VkDeviceSize[1]) { op->crossfade.vertex_offset });
+              current_draw_index = 0;
+            }
+
+          vkCmdBindDescriptorSets (command_buffer,
+                                   VK_PIPELINE_BIND_POINT_GRAPHICS,
+                                   gsk_vulkan_pipeline_get_pipeline_layout (current_pipeline),
+                                   0,
+                                   2,
+                                   (VkDescriptorSet[2]) {
+                                       gsk_vulkan_render_get_descriptor_set (render, op->crossfade.descriptor_set_start),
+                                       gsk_vulkan_render_get_descriptor_set (render, op->crossfade.descriptor_set_end)
+                                   },
+                                   0,
+                                   NULL);
+
+          current_draw_index += gsk_vulkan_blend_mode_pipeline_draw (GSK_VULKAN_BLEND_MODE_PIPELINE (current_pipeline),
+                                                                     command_buffer,
+                                                                     current_draw_index, 1);
+          break;
+
         default:
           g_assert_not_reached ();
           break;
diff --git a/gsk/gskvulkanrenderprivate.h b/gsk/gskvulkanrenderprivate.h
index 6739bb5941..ed35019c3f 100644
--- a/gsk/gskvulkanrenderprivate.h
+++ b/gsk/gskvulkanrenderprivate.h
@@ -43,6 +43,9 @@ typedef enum {
   GSK_VULKAN_PIPELINE_CROSS_FADE,
   GSK_VULKAN_PIPELINE_CROSS_FADE_CLIP,
   GSK_VULKAN_PIPELINE_CROSS_FADE_CLIP_ROUNDED,
+  GSK_VULKAN_PIPELINE_BLEND_MODE,
+  GSK_VULKAN_PIPELINE_BLEND_MODE_CLIP,
+  GSK_VULKAN_PIPELINE_BLEND_MODE_CLIP_ROUNDED,
   /* add more */
   GSK_VULKAN_N_PIPELINES
 } GskVulkanPipelineType;
diff --git a/gsk/meson.build b/gsk/meson.build
index 072c140da3..e91985af8e 100644
--- a/gsk/meson.build
+++ b/gsk/meson.build
@@ -54,6 +54,7 @@ gsk_private_vulkan_compiled_shaders_deps = []
 
 if have_vulkan
   gsk_private_sources += files([
+    'gskvulkanblendmodepipeline.c',
     'gskvulkanblendpipeline.c',
     'gskvulkanblurpipeline.c',
     'gskvulkanborderpipeline.c',
diff --git a/gsk/resources/vulkan/blendmode-clip-rounded.frag.spv b/gsk/resources/vulkan/blendmode-clip-rounded.frag.spv
new file mode 100644
index 0000000000..4ede20eb07
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode-clip-rounded.frag.spv
diff --git a/gsk/resources/vulkan/blendmode-clip-rounded.vert.spv b/gsk/resources/vulkan/blendmode-clip-rounded.vert.spv
new file mode 100644
index 0000000000..499a74abe1
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode-clip-rounded.vert.spv
diff --git a/gsk/resources/vulkan/blendmode-clip.frag.spv b/gsk/resources/vulkan/blendmode-clip.frag.spv
new file mode 100644
index 0000000000..21484c8e18
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode-clip.frag.spv
diff --git a/gsk/resources/vulkan/blendmode-clip.vert.spv b/gsk/resources/vulkan/blendmode-clip.vert.spv
new file mode 100644
index 0000000000..499a74abe1
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode-clip.vert.spv
diff --git a/gsk/resources/vulkan/blendmode-rect-rounded.frag.spv b/gsk/resources/vulkan/blendmode-rect-rounded.frag.spv
new file mode 100644
index 0000000000..55ce955e83
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode-rect-rounded.frag.spv
diff --git a/gsk/resources/vulkan/blendmode-rect.frag.spv b/gsk/resources/vulkan/blendmode-rect.frag.spv
new file mode 100644
index 0000000000..7d0fdd1fa7
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode-rect.frag.spv
diff --git a/gsk/resources/vulkan/blendmode.frag b/gsk/resources/vulkan/blendmode.frag
new file mode 100644
index 0000000000..803a538d1d
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode.frag
@@ -0,0 +1,183 @@
+#version 420 core
+
+#include "clip.frag.glsl"
+
+layout(location = 0) in vec2 inPos;
+layout(location = 1) in vec2 inStartTexCoord;
+layout(location = 2) in vec2 inEndTexCoord;
+layout(location = 3) flat in uint inBlendMode;
+
+layout(set = 0, binding = 0) uniform sampler2D startTexture;
+layout(set = 1, binding = 0) uniform sampler2D endTexture;
+
+layout(location = 0) out vec4 color;
+
+vec3
+multiply (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = source * backdrop;
+  return mix (source, result, opacity);
+}
+
+vec3
+difference (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = abs (source - backdrop);
+  return mix (source, result, opacity);
+}
+
+vec3
+screen (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = source + backdrop - source * backdrop;
+  return mix (source, result, opacity);
+}
+
+float
+hard_light (float source, float backdrop)
+{
+  if (source <= 0.5)
+    return 2 * backdrop * source;
+  else
+    return 2 * (backdrop + source - backdrop * source) - 1;
+}
+
+vec3
+hard_light (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = vec3 (hard_light (source.r, backdrop.r),
+                      hard_light (source.g, backdrop.g),
+                      hard_light (source.b, backdrop.b));
+  return mix (source, result, opacity);
+}
+
+float
+soft_light (float source, float backdrop)
+{
+  float db;
+
+  if (backdrop <= 0.25)
+    db = ((16 * backdrop - 12) * backdrop + 4) * backdrop;
+  else
+    db = sqrt (backdrop);
+
+  if (source <= 0.5)
+    return backdrop - (1 - 2 * source) * backdrop * (1 - backdrop);
+  else
+    return backdrop + (2 * source - 1) * (db - backdrop);
+}
+
+vec3
+soft_light (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = vec3 (soft_light (source.r, backdrop.r),
+                      soft_light (source.g, backdrop.g),
+                      soft_light (source.b, backdrop.b));
+  return mix (source, result, opacity);
+}
+
+vec3
+overlay (vec3 source, vec3 backdrop, float opacity)
+{
+  return hard_light (backdrop, source, opacity);
+}
+
+vec3
+darken (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = min (source, backdrop);
+  return mix (source, result, opacity);
+}
+
+vec3
+lighten (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = max (source, backdrop);
+  return mix (source, result, opacity);
+}
+
+float
+color_dodge (float source, float backdrop)
+{
+  return (source == 1.0) ? source : min (backdrop / (1.0 - source), 1.0);
+}
+
+vec3
+color_dodge (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = vec3 (color_dodge (source.r, backdrop.r),
+                      color_dodge (source.g, backdrop.g),
+                      color_dodge (source.b, backdrop.b));
+  return mix (source, result, opacity);
+}
+
+
+float
+color_burn (float source, float backdrop)
+{
+  return (source == 0.0) ? source : max ((1.0 - ((1.0 - backdrop) / source)), 0.0);
+}
+
+vec3
+color_burn (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = vec3 (color_burn (source.r, backdrop.r),
+                      color_burn (source.g, backdrop.g),
+                      color_burn (source.b, backdrop.b));
+  return mix (source, result, opacity);
+}
+
+vec3
+exclusion (vec3 source, vec3 backdrop, float opacity)
+{
+  vec3 result = backdrop + source - 2.0 * backdrop * source;
+  return mix (source, result, opacity);
+}
+
+float
+combine (float source, float backdrop)
+{
+  return source + backdrop * (1 - source);
+}
+
+void main()
+{
+  vec4 source = texture (startTexture, inStartTexCoord);
+  vec4 backdrop = texture (endTexture, inEndTexCoord);
+  vec3 rgb = vec3(1,0,0);
+  float a = 1;
+
+  a = combine (source.a, backdrop.a);
+
+  if (inBlendMode == 0) // default
+    {
+      rgb = source.rgb;
+      a = source.a;
+    }
+  else if (inBlendMode == 1)
+    rgb = multiply (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 2)
+    rgb = screen (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 3)
+    rgb = overlay (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 4)
+    rgb = darken (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 5)
+    rgb = lighten (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 6)
+    rgb = color_dodge (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 7)
+    rgb = color_burn (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 8)
+    rgb = hard_light (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 9)
+    rgb = soft_light (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 10)
+    rgb = difference (source.rgb, backdrop.rgb, backdrop.a);
+  else if (inBlendMode == 11)
+    rgb = exclusion (source.rgb, backdrop.rgb, backdrop.a);
+  else
+    discard;
+
+  color = clip (inPos, vec4 (rgb, a));
+}
diff --git a/gsk/resources/vulkan/blendmode.frag.spv b/gsk/resources/vulkan/blendmode.frag.spv
new file mode 100644
index 0000000000..21484c8e18
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode.frag.spv
diff --git a/gsk/resources/vulkan/blendmode.vert b/gsk/resources/vulkan/blendmode.vert
new file mode 100644
index 0000000000..35b8356c90
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode.vert
@@ -0,0 +1,44 @@
+#version 420 core
+
+#include "clip.vert.glsl"
+
+layout(location = 0) in vec4 inRect;
+layout(location = 1) in vec4 inStartTexRect;
+layout(location = 2) in vec4 inEndTexRect;
+layout(location = 3) in uint inBlendMode;
+
+layout(location = 0) out vec2 outPos;
+layout(location = 1) out vec2 outStartTexCoord;
+layout(location = 2) out vec2 outEndTexCoord;
+layout(location = 3) flat out uint outBlendMode;
+
+out gl_PerVertex {
+  vec4 gl_Position;
+};
+
+vec2 offsets[6] = { vec2(0.0, 0.0),
+                    vec2(1.0, 0.0),
+                    vec2(0.0, 1.0),
+                    vec2(0.0, 1.0),
+                    vec2(1.0, 0.0),
+                    vec2(1.0, 1.0) };
+
+void main() {
+  vec4 rect = clip (inRect);
+  vec2 pos = rect.xy + rect.zw * offsets[gl_VertexIndex];
+  gl_Position = push.mvp * vec4 (pos, 0.0, 1.0);
+
+  outPos = pos;
+
+  vec4 texrect = vec4((rect.xy - inRect.xy) / inRect.zw,
+                      rect.zw / inRect.zw);
+  vec4 starttexrect = vec4(inStartTexRect.xy + inStartTexRect.zw * texrect.xy,
+                           inStartTexRect.zw * texrect.zw);
+  vec4 endtexrect = vec4(inEndTexRect.xy + inEndTexRect.zw * texrect.xy,
+                         inEndTexRect.zw * texrect.zw);
+
+  outStartTexCoord = starttexrect.xy + starttexrect.zw * offsets[gl_VertexIndex];
+  outEndTexCoord = endtexrect.xy + endtexrect.zw * offsets[gl_VertexIndex];
+
+  outBlendMode = inBlendMode;
+}
diff --git a/gsk/resources/vulkan/blendmode.vert.spv b/gsk/resources/vulkan/blendmode.vert.spv
new file mode 100644
index 0000000000..614f7cfc50
--- /dev/null
+++ b/gsk/resources/vulkan/blendmode.vert.spv
diff --git a/gsk/resources/vulkan/meson.build b/gsk/resources/vulkan/meson.build
index 6e61885e65..160bc0d6e4 100644
--- a/gsk/resources/vulkan/meson.build
+++ b/gsk/resources/vulkan/meson.build
@@ -8,6 +8,7 @@
 
 gsk_private_vulkan_fragment_shaders = [
   'blend.frag',
+  'blendmode.frag',
   'blur.frag',
   'border.frag',
   'color.frag',
@@ -21,6 +22,7 @@ gsk_private_vulkan_fragment_shaders = [
 
 gsk_private_vulkan_vertex_shaders = [
   'blend.vert',
+  'blendmode.vert',
   'blur.vert',
   'border.vert',
   'color.vert',