[core] add ability to render to offscreen textures

1 files changed, 66 insertions, 0 deletions

diff --git a/src/mbgl/util/offscreen_texture.cpp b/src/mbgl/util/offscreen_texture.cpp
new file mode 100644
index 0000000000..e077d60572
--- /dev/null
+++ b/src/mbgl/util/offscreen_texture.cpp
@@ -0,0 +1,66 @@
+#include <mbgl/gl/gl_config.hpp>
+#include <mbgl/util/offscreen_texture.hpp>
+
+#include <cassert>
+
+namespace mbgl {
+
+void OffscreenTexture::bind(gl::ObjectStore& store,
+                            gl::Config& config,
+                            std::array<uint16_t, 2> size) {
+    assert(size[0] > 0 && size[1] > 0);
+
+    if (raster.getSize() != size) {
+        raster.load(PremultipliedImage(size[0], size[1], nullptr));
+        raster.upload(store, config, 0);
+    }
+
+    if (!fbo) {
+        fbo = store.createFBO();
+        config.bindFramebuffer = *fbo;
+        MBGL_CHECK_ERROR(glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
+                                                raster.getID(), 0));
+
+        GLenum status = MBGL_CHECK_ERROR(glCheckFramebufferStatus(GL_FRAMEBUFFER));
+        if (status != GL_FRAMEBUFFER_COMPLETE) {
+            switch (status) {
+            case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
+                throw std::runtime_error("Couldn't create framebuffer: incomplete attachment");
+            case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
+                throw std::runtime_error(
+                    "Couldn't create framebuffer: incomplete missing attachment");
+#ifdef GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER
+            case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER:
+                throw std::runtime_error("Couldn't create framebuffer: incomplete draw buffer");
+#endif
+#ifdef GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER
+            case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER:
+                throw std::runtime_error("Couldn't create framebuffer: incomplete read buffer");
+#endif
+#ifdef GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS
+            case GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS:
+                throw std::runtime_error("Couldn't create framebuffer: incomplete dimensions");
+#endif
+
+            case GL_FRAMEBUFFER_UNSUPPORTED:
+                throw std::runtime_error("Couldn't create framebuffer: unsupported");
+            default:
+                throw std::runtime_error("Couldn't create framebuffer: other");
+            }
+        }
+    } else {
+        config.bindFramebuffer = *fbo;
+    }
+
+    config.viewport = { { 0, 0, static_cast<GLint>(size[0]), static_cast<GLint>(size[1]) } };
+}
+
+Raster& OffscreenTexture::getTexture() {
+    return raster;
+}
+
+std::array<uint16_t, 2> OffscreenTexture::getSize() const {
+    return raster.getSize();
+}
+
+} // namespace mbgl