[core] Implement MapDebugOptions::Wireframe

Together with MapDebugOptions::Collision, provides "wireframe" rendering
output so all drawn objects are visible. This mode ignores the line
width, background and fill colors for better visualization.

Fixes #4359.

5 files changed, 50 insertions, 22 deletions

diff --git a/src/mbgl/map/map.cpp b/src/mbgl/map/map.cpp
index 0a6adfc565..fc2a653510 100644
--- a/src/mbgl/map/map.cpp
+++ b/src/mbgl/map/map.cpp
@@ -796,8 +796,10 @@ void Map::setDebug(MapDebugOptions debugOptions) {
 }
 
 void Map::cycleDebugOptions() {
-    if (impl->debugOptions & MapDebugOptions::Collision)
+    if (impl->debugOptions & MapDebugOptions::Wireframe)
         impl->debugOptions = MapDebugOptions::NoDebug;
+    else if (impl->debugOptions & MapDebugOptions::Collision)
+        impl->debugOptions = MapDebugOptions::Collision | MapDebugOptions::Wireframe;
     else if (impl->debugOptions & MapDebugOptions::Timestamps)
         impl->debugOptions = impl->debugOptions | MapDebugOptions::Collision;
     else if (impl->debugOptions & MapDebugOptions::ParseStatus)
diff --git a/src/mbgl/renderer/painter.cpp b/src/mbgl/renderer/painter.cpp
index 175770dbb1..b03e4d1afe 100644
--- a/src/mbgl/renderer/painter.cpp
+++ b/src/mbgl/renderer/painter.cpp
@@ -141,7 +141,11 @@ void Painter::render(const Style& style, const FrameData& frame_, SpriteAtlas& a
         config.depthTest = GL_FALSE;
         config.depthMask = GL_TRUE;
         config.colorMask = { GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE };
-        config.clearColor = { background[0], background[1], background[2], background[3] };
+        if (frame.debugOptions & MapDebugOptions::Wireframe) {
+            config.clearColor = { 0.0f, 0.0f, 0.0f, 1.0f };
+        } else {
+            config.clearColor = { background[0], background[1], background[2], background[3] };
+        }
         config.clearStencil = 0;
         config.clearDepth = 1;
         MBGL_CHECK_ERROR(glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT | GL_DEPTH_BUFFER_BIT));
diff --git a/src/mbgl/renderer/painter_background.cpp b/src/mbgl/renderer/painter_background.cpp
index e71e9677d1..5054722e79 100644
--- a/src/mbgl/renderer/painter_background.cpp
+++ b/src/mbgl/renderer/painter_background.cpp
@@ -14,10 +14,13 @@ void Painter::renderBackground(const BackgroundLayer& layer) {
     // glClear rather than this method.
     const BackgroundPaintProperties& properties = layer.paint;
 
-    const bool isPatterned = !properties.backgroundPattern.value.to.empty();// && false;
+    bool isPatterned = !properties.backgroundPattern.value.to.empty();// && false;
     optional<SpriteAtlasPosition> imagePosA;
     optional<SpriteAtlasPosition> imagePosB;
 
+    bool wireframe = frame.debugOptions & MapDebugOptions::Wireframe;
+    isPatterned &= !wireframe;
+
     if (isPatterned) {
         imagePosA = spriteAtlas->getPosition(properties.backgroundPattern.value.from, true);
         imagePosB = spriteAtlas->getPosition(properties.backgroundPattern.value.to, true);
@@ -38,14 +41,18 @@ void Painter::renderBackground(const BackgroundLayer& layer) {
         backgroundPatternArray.bind(*patternShader, tileStencilBuffer, BUFFER_OFFSET(0), glObjectStore);
 
     } else {
-        Color color = properties.backgroundColor;
-        color[0] *= properties.backgroundOpacity;
-        color[1] *= properties.backgroundOpacity;
-        color[2] *= properties.backgroundOpacity;
-        color[3] *= properties.backgroundOpacity;
+        if (wireframe) {
+            plainShader->u_color = {{ 0.0f, 0.0f, 0.0f, 1.0f }};
+        } else {
+            Color color = properties.backgroundColor;
+            color[0] *= properties.backgroundOpacity;
+            color[1] *= properties.backgroundOpacity;
+            color[2] *= properties.backgroundOpacity;
+            color[3] *= properties.backgroundOpacity;
+            plainShader->u_color = color;
+        }
 
         config.program = plainShader->getID();
-        plainShader->u_color = color;
         backgroundArray.bind(*plainShader, tileStencilBuffer, BUFFER_OFFSET(0), glObjectStore);
     }
 
@@ -99,8 +106,11 @@ void Painter::renderBackground(const BackgroundLayer& layer) {
 
         } else {
             plainShader->u_matrix = vtxMatrix;
-            Color color = properties.backgroundColor;
-            plainShader->u_color = color;
+            if (wireframe) {
+                plainShader->u_color = {{ 0.0f, 0.0f, 0.0f, 1.0f }};
+            } else {
+                plainShader->u_color = properties.backgroundColor;
+            }
         }
 
         MBGL_CHECK_ERROR(glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)tileStencilBuffer.index()));
diff --git a/src/mbgl/renderer/painter_fill.cpp b/src/mbgl/renderer/painter_fill.cpp
index 2e103462e6..1ac90a2806 100644
--- a/src/mbgl/renderer/painter_fill.cpp
+++ b/src/mbgl/renderer/painter_fill.cpp
@@ -33,11 +33,19 @@ void Painter::renderFill(FillBucket& bucket,
         stroke_color[3] *= properties.fillOpacity;
     }
 
-    const bool pattern = !properties.fillPattern.value.from.empty();
-
+    bool pattern = !properties.fillPattern.value.from.empty();
     bool outline = properties.fillAntialias && !pattern && stroke_color != fill_color;
     bool fringeline = properties.fillAntialias && !pattern && stroke_color == fill_color;
 
+    bool wireframe = frame.debugOptions & MapDebugOptions::Wireframe;
+    if (wireframe) {
+        fill_color = {{ 1.0f, 1.0f, 1.0f, 1.0f }};
+        stroke_color = {{ 1.0f, 1.0f, 1.0f, 1.0f }};
+        pattern = false;
+        outline = true;
+        fringeline = true;
+    }
+
     config.stencilOp.reset();
     config.stencilTest = GL_TRUE;
     config.depthFunc.reset();
@@ -154,8 +162,7 @@ void Painter::renderFill(FillBucket& bucket,
                 bucket.drawVertices(*outlinePatternShader, glObjectStore);
             }
         }
-    }
-    else {
+    } else if (!wireframe) {
         // No image fill.
         if ((fill_color[3] >= 1.0f) == (pass == RenderPass::Opaque)) {
             // Only draw the fill when it's either opaque and we're drawing opaque
diff --git a/src/mbgl/renderer/painter_line.cpp b/src/mbgl/renderer/painter_line.cpp
index 6adf471cef..c0706dcdd7 100644
--- a/src/mbgl/renderer/painter_line.cpp
+++ b/src/mbgl/renderer/painter_line.cpp
@@ -30,13 +30,15 @@ void Painter::renderLine(LineBucket& bucket,
     // Retina devices need a smaller distance to avoid aliasing.
     float antialiasing = 1.0 / frame.pixelRatio;
 
+    bool wireframe = frame.debugOptions & MapDebugOptions::Wireframe;
+
     float blur = properties.lineBlur + antialiasing;
-    float edgeWidth = properties.lineWidth / 2.0;
+    float edgeWidth = wireframe ? 1 : properties.lineWidth / 2.0;
     float inset = -1;
     float offset = 0;
     float shift = 0;
 
-    if (properties.lineGapWidth != 0) {
+    if (properties.lineGapWidth != 0 && !wireframe) {
         inset = properties.lineGapWidth / 2.0 + antialiasing * 0.5;
         edgeWidth = properties.lineWidth;
 
@@ -46,11 +48,14 @@ void Painter::renderLine(LineBucket& bucket,
 
     float outset = offset + edgeWidth + antialiasing / 2.0 + shift;
 
-    Color color = properties.lineColor;
-    color[0] *= properties.lineOpacity;
-    color[1] *= properties.lineOpacity;
-    color[2] *= properties.lineOpacity;
-    color[3] *= properties.lineOpacity;
+    Color color = {{ 1.0f, 1.0f, 1.0f, 1.0f }};
+    if (!wireframe) {
+        color = properties.lineColor;
+        color[0] *= properties.lineOpacity;
+        color[1] *= properties.lineOpacity;
+        color[2] *= properties.lineOpacity;
+        color[3] *= properties.lineOpacity;
+    }
 
     const float ratio = 1.0 / tileID.pixelsToTileUnits(1.0, state.getZoom());