[core] generate masks for raster tiles to avoid painting over children

cmake/core-files.cmake

@@ -199,6 +199,8 @@ set(MBGL_CORE_FILES
     src/mbgl/renderer/style_diff.cpp
     src/mbgl/renderer/style_diff.hpp
     src/mbgl/renderer/tile_mask.hpp
+    src/mbgl/renderer/tile_mask_repository.cpp
+    src/mbgl/renderer/tile_mask_repository.hpp
     src/mbgl/renderer/tile_parameters.hpp
     src/mbgl/renderer/tile_pyramid.cpp
     src/mbgl/renderer/tile_pyramid.hpp

cmake/test-files.cmake

@@ -45,6 +45,7 @@ set(MBGL_TEST_FILES
     # renderer
     test/renderer/group_by_layout.test.cpp
     test/renderer/image_manager.test.cpp
+    test/renderer/tile_mask_repository.test.cpp
 
     # sprite
     test/sprite/sprite_loader.test.cpp

src/mbgl/renderer/buckets/raster_bucket.cpp

@@ -33,7 +33,7 @@ void RasterBucket::render(Painter& painter,
                           const RenderLayer& layer,
                           const RenderTile& tile) {
     painter.renderRaster(parameters, *this, *layer.as<RenderRasterLayer>(), tile.matrix,
-                         painter.rasterDrawable);
+                         painter.tileMaskRepository.getDrawable(painter.context, tile.mask));
 }
 
 void RasterBucket::render(Painter& painter,

src/mbgl/renderer/painter.cpp

@@ -43,22 +43,6 @@ namespace mbgl {
 
 using namespace style;
 
-static auto rasterPrimitives() {
-    IndexedPrimitives<gl::Triangles, RasterLayoutVertex, RasterAttributes> primitives;
-    primitives.add(
-        {
-            RasterProgram::layoutVertex({ 0,            0            }, { 0,     0 }),
-            RasterProgram::layoutVertex({ util::EXTENT, 0            }, { 32767, 0 }),
-            RasterProgram::layoutVertex({ 0,            util::EXTENT }, { 0,     32767 }),
-            RasterProgram::layoutVertex({ util::EXTENT, util::EXTENT }, { 32767, 32767 }),
-        }, {
-            {{ 0, 1, 2 }},
-            {{ 1, 2, 3 }},
-        }
-    );
-    return primitives;
-}
-
 static auto borderPrimitives() {
     IndexedPrimitives<gl::LineStrip, DebugLayoutVertex, DebugAttributes> primitives;
     primitives.add(
@@ -116,7 +100,6 @@ Painter::Painter(gl::Context& context_,
                  const optional<std::string>& programCacheDir)
     : context(context_),
       state(state_),
-      rasterDrawable(context, rasterPrimitives()),
       fillDrawable(context, fillPrimitives()),
       borderDrawable(context, borderPrimitives()),
       extrusionTextureDrawable(context, extrusionTexturePrimitives()) {

src/mbgl/renderer/painter.hpp

@@ -9,6 +9,7 @@
 #include <mbgl/renderer/bucket.hpp>
 #include <mbgl/renderer/render_light.hpp>
 #include <mbgl/renderer/drawable.hpp>
+#include <mbgl/renderer/tile_mask_repository.hpp>
 
 #include <mbgl/gl/context.hpp>
 #include <mbgl/programs/debug_program.hpp>
@@ -168,7 +169,7 @@ class Painter : private util::noncopyable {
     std::unique_ptr<Programs> overdrawPrograms;
 #endif
 
-    const Drawable<gl::Triangles, RasterLayoutVertex, RasterAttributes> rasterDrawable;
+    TileMaskRepository tileMaskRepository;
     const Drawable<gl::Triangles, FillLayoutVertex, FillAttributes> fillDrawable;
     const Drawable<gl::LineStrip, DebugLayoutVertex, DebugAttributes> borderDrawable;
     const Drawable<gl::Triangles, ExtrusionTextureLayoutVertex, ExtrusionTextureAttributes> extrusionTextureDrawable;

src/mbgl/renderer/render_tile.hpp

@@ -4,6 +4,7 @@
 #include <mbgl/util/mat4.hpp>
 #include <mbgl/util/clip_id.hpp>
 #include <mbgl/style/types.hpp>
+#include <mbgl/renderer/tile_mask.hpp>
 
 #include <array>
 
@@ -24,6 +25,7 @@ class RenderTile final {
     const UnwrappedTileID id;
     Tile& tile;
     ClipID clip;
+    TileMask mask;
     mat4 matrix;
     mat4 nearClippedMatrix;
     bool used = false;

src/mbgl/renderer/sources/render_raster_source.cpp

@@ -1,6 +1,7 @@
 #include <mbgl/renderer/sources/render_raster_source.hpp>
 #include <mbgl/renderer/render_tile.hpp>
 #include <mbgl/tile/raster_tile.hpp>
+#include <mbgl/algorithm/update_tile_masks.hpp>
 
 namespace mbgl {
 
@@ -57,6 +58,7 @@ void RenderRasterSource::update(Immutable<style::Source::Impl> baseImpl_,
 }
 
 void RenderRasterSource::startRender(Painter& painter) {
+    algorithm::updateTileMasks(tilePyramid.getRenderTiles());
     tilePyramid.startRender(painter);
 }
 

src/mbgl/renderer/tile_mask.hpp

@@ -6,6 +6,10 @@
 
 namespace mbgl {
 
+// A TileMask is a set of TileIDs that describe what part of a tile should be rendered. I.e. it
+// denotes the part of a tile that is covered by other/better tiles. If the entire tile should be
+// rendered, it contains the { 0, 0, 0 } tile. If it's empty, no part of the tile will be rendered.
+// TileMasks are typically generated with algorithm::updateTileMasks().
 using TileMask = std::set<CanonicalTileID>;
 
 } // namespace mbgl

src/mbgl/renderer/tile_mask_repository.cpp

@@ -0,0 +1,60 @@
+#include <mbgl/renderer/tile_mask_repository.hpp>
+#include <mbgl/util/constants.hpp>
+
+namespace mbgl {
+
+const Drawable<gl::Triangles, RasterLayoutVertex, RasterAttributes>&
+TileMaskRepository::getDrawable(gl::Context& context, const TileMask& mask) {
+    auto it = drawables.find(mask);
+    if (it == drawables.end()) {
+        it = drawables
+                 .emplace(std::piecewise_construct, std::forward_as_tuple(mask),
+                          std::forward_as_tuple(context, getPrimitives(mask)))
+                 .first;
+    }
+    return it->second;
+}
+
+void TileMaskRepository::clear() {
+    drawables.clear();
+}
+
+IndexedPrimitives<gl::Triangles, RasterLayoutVertex, RasterAttributes>
+TileMaskRepository::getPrimitives(const TileMask& mask) {
+    IndexedPrimitives<gl::Triangles, RasterLayoutVertex, RasterAttributes> primitives;
+
+    for (const auto& id : mask) {
+        // Create a quad for every masked tile.
+        const int32_t vertexExtent = util::EXTENT >> id.z;
+        const int32_t textureExtent = 32768 >> id.z;
+
+        const Point<int16_t> tlVertex = { static_cast<int16_t>(id.x * vertexExtent),
+                                          static_cast<int16_t>(id.y * vertexExtent) };
+        const Point<int16_t> brVertex = { static_cast<int16_t>(tlVertex.x + vertexExtent),
+                                          static_cast<int16_t>(tlVertex.y + vertexExtent) };
+        const Point<uint16_t> tlTexture = { static_cast<uint16_t>(id.x * textureExtent),
+                                            static_cast<uint16_t>(id.y * textureExtent) };
+        const Point<uint16_t> brTexture = { static_cast<uint16_t>(tlTexture.x + textureExtent),
+                                            static_cast<uint16_t>(tlTexture.y + textureExtent) };
+
+        primitives.add(
+            {
+                RasterProgram::layoutVertex({ tlVertex.x, tlVertex.y },
+                                            { tlTexture.x, tlTexture.y }),
+                RasterProgram::layoutVertex({ brVertex.x, tlVertex.y },
+                                            { brTexture.x, tlTexture.y }),
+                RasterProgram::layoutVertex({ tlVertex.x, brVertex.y },
+                                            { tlTexture.x, brTexture.y }),
+                RasterProgram::layoutVertex({ brVertex.x, brVertex.y },
+                                            { brTexture.x, brTexture.y }),
+            },
+            {
+                {{ 0, 1, 2 }},
+                {{ 1, 2, 3 }},
+            });
+    }
+
+    return primitives;
+}
+
+} // namespace mbgl

src/mbgl/renderer/tile_mask_repository.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <mbgl/renderer/tile_mask.hpp>
+#include <mbgl/renderer/indexed_primitives.hpp>
+#include <mbgl/renderer/drawable.hpp>
+#include <mbgl/gl/draw_mode.hpp>
+#include <mbgl/programs/raster_program.hpp>
+
+namespace mbgl {
+
+namespace gl {
+class Context;
+} // namespace gl
+
+class TileMaskRepository {
+public:
+    const Drawable<gl::Triangles, RasterLayoutVertex, RasterAttributes>&
+    getDrawable(gl::Context&, const TileMask&);
+
+    void clear();
+
+    static IndexedPrimitives<gl::Triangles, RasterLayoutVertex, RasterAttributes>
+    getPrimitives(const TileMask&);
+
+private:
+    std::map<TileMask, const Drawable<gl::Triangles, RasterLayoutVertex, RasterAttributes>> drawables;
+};
+
+} // namespace mbgl