Enable point sample when the texel and pixel is 1:1 mapping.

Change-Id: I532ad6b038d3b141bd212c8c408533fec0e9616e

7 files changed, 48 insertions, 9 deletions

diff --git a/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.cpp b/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.cpp
index 40bf0be..b1fe2f4 100644
--- a/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.cpp
@@ -40,6 +40,8 @@
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
 
+#define EPSILON 0.00001f
+
 namespace WebCore {
 
 static const char gVertexShader[] =
@@ -736,6 +738,36 @@ void ShaderProgram::setGLDrawInfo(const android::uirenderer::DrawGlInfo* info)
     m_targetHeight = info->height;
 }
 
+// This function is called per tileGrid to minimize the computation overhead.
+// The ortho projection and glViewport will map 1:1, so we don't need to
+// worry about them here. Basically, if the current zoom scale / tile's scale
+// plus the webview and layer transformation ends up at scale factor 1.0,
+// then we can use point sampling.
+bool ShaderProgram::usePointSampling(float tileScale,
+                                     const TransformationMatrix* layerTransform)
+{
+    const float testSize = 1.0;
+    FloatRect rect(0, 0, testSize, testSize);
+    TransformationMatrix matrix;
+    matrix.scale3d(m_currentScale, m_currentScale, 1);
+    if (layerTransform)
+        matrix.multiply(*layerTransform);
+    matrix.scale3d(1.0 / tileScale, 1.0 / tileScale, 1);
+
+    matrix = m_webViewMatrix * matrix;
+
+    rect = matrix.mapRect(rect);
+
+    float deltaWidth = abs(rect.width() - testSize);
+    float deltaHeight = abs(rect.height() - testSize);
+
+    if (deltaWidth < EPSILON && deltaHeight < EPSILON) {
+        ALOGV("Point sampling : deltaWidth is %f, deltaHeight is %f", deltaWidth, deltaHeight);
+        return true;
+    }
+    return false;
+}
+
 #if DEBUG_MATRIX
 FloatRect ShaderProgram::debugMatrixTransform(const TransformationMatrix& matrix,
                                               const char* matrixName)
diff --git a/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.h b/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.h
index b44c563..cfdccda 100644
--- a/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.h
+++ b/Source/WebCore/platform/graphics/android/rendering/ShaderProgram.h
@@ -155,6 +155,7 @@ public:
     void setGLDrawInfo(const android::uirenderer::DrawGlInfo* info);
 
     bool needsInit() { return m_needsInit; }
+    bool usePointSampling(float tileScale, const TransformationMatrix* layerTransform);
 
 private:
     GLuint loadShader(GLenum shaderType, const char* pSource);
diff --git a/Source/WebCore/platform/graphics/android/rendering/Tile.cpp b/Source/WebCore/platform/graphics/android/rendering/Tile.cpp
index 178958d..f2aa9a0 100644
--- a/Source/WebCore/platform/graphics/android/rendering/Tile.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/Tile.cpp
@@ -209,7 +209,7 @@ void Tile::setRepaintPending(bool pending)
 
 bool Tile::drawGL(float opacity, const SkRect& rect, float scale,
                   const TransformationMatrix* transform,
-                  bool forceBlending)
+                  bool forceBlending, bool usePointSampling)
 {
     if (m_x < 0 || m_y < 0 || m_scale != scale)
         return false;
@@ -219,7 +219,8 @@ bool Tile::drawGL(float opacity, const SkRect& rect, float scale,
     if (!m_frontTexture)
         return false;
 
-    m_frontTexture->drawGL(isLayerTile(), rect, opacity, transform, forceBlending);
+    m_frontTexture->drawGL(isLayerTile(), rect, opacity, transform,
+                           forceBlending, usePointSampling);
     return true;
 }
 
diff --git a/Source/WebCore/platform/graphics/android/rendering/Tile.h b/Source/WebCore/platform/graphics/android/rendering/Tile.h
index cc10799..fa06892 100644
--- a/Source/WebCore/platform/graphics/android/rendering/Tile.h
+++ b/Source/WebCore/platform/graphics/android/rendering/Tile.h
@@ -102,7 +102,7 @@ public:
     // Return false when real draw didn't happen for any reason.
     bool drawGL(float opacity, const SkRect& rect, float scale,
                 const TransformationMatrix* transform,
-                bool forceBlending = false);
+                bool forceBlending = false, bool usePointSampling = false);
 
     // the only thread-safe function called by the background thread
     void paintBitmap(TilePainter* painter);
diff --git a/Source/WebCore/platform/graphics/android/rendering/TileGrid.cpp b/Source/WebCore/platform/graphics/android/rendering/TileGrid.cpp
index 00cc656..ad305b7 100644
--- a/Source/WebCore/platform/graphics/android/rendering/TileGrid.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/TileGrid.cpp
@@ -296,6 +296,9 @@ void TileGrid::drawGL(const IntRect& visibleArea, float opacity,
         missingRegion = SkRegion(totalArea);
     }
 
+    bool usePointSampling =
+        TilesManager::instance()->shader()->usePointSampling(m_scale, transform);
+
     for (unsigned int i = 0; i < m_tiles.size(); i++) {
         Tile* tile = m_tiles[i];
 
@@ -312,7 +315,7 @@ void TileGrid::drawGL(const IntRect& visibleArea, float opacity,
 
             bool forceBaseBlending = background ? background->hasAlpha() : false;
             bool success = tile->drawGL(opacity, rect, m_scale, transform,
-                                        forceBaseBlending);
+                                        forceBaseBlending, usePointSampling);
             if (semiOpaqueBaseSurface && success) {
                 // Cut the successful drawn tile area from the missing region.
                 missingRegion.op(SkIRect::MakeXYWH(tile->x(), tile->y(), 1, 1),
diff --git a/Source/WebCore/platform/graphics/android/rendering/TileTexture.cpp b/Source/WebCore/platform/graphics/android/rendering/TileTexture.cpp
index 126a7ac..3dceda9 100644
--- a/Source/WebCore/platform/graphics/android/rendering/TileTexture.cpp
+++ b/Source/WebCore/platform/graphics/android/rendering/TileTexture.cpp
@@ -120,7 +120,7 @@ void TileTexture::transferComplete()
 
 void TileTexture::drawGL(bool isLayer, const SkRect& rect, float opacity,
                          const TransformationMatrix* transform,
-                         bool forceBlending)
+                         bool forceBlending, bool usePointSampling)
 {
     ShaderProgram* shader = TilesManager::instance()->shader();
 
@@ -132,14 +132,15 @@ void TileTexture::drawGL(bool isLayer, const SkRect& rect, float opacity,
     // For base layer, we just follow the forceBlending, otherwise, blending is
     // always turned on.
     // TODO: Don't blend tiles if they are fully opaque.
-    forceBlending |= isLayer;
+    bool useBlending = forceBlending || isLayer;
     DrawQuadData commonData(isLayer ? LayerQuad : BaseQuad, transform, &rect,
-                            opacity, forceBlending);
+                            opacity, useBlending);
     if (isPureColor()) {
         PureColorQuadData data(commonData, pureColor());
         shader->drawQuad(&data);
     } else {
-        TextureQuadData data(commonData, m_ownTextureId, GL_TEXTURE_2D, GL_LINEAR);
+        GLint filter = usePointSampling ? GL_NEAREST : GL_LINEAR;
+        TextureQuadData data(commonData, m_ownTextureId, GL_TEXTURE_2D, filter);
         shader->drawQuad(&data);
     }
 }
diff --git a/Source/WebCore/platform/graphics/android/rendering/TileTexture.h b/Source/WebCore/platform/graphics/android/rendering/TileTexture.h
index b008b7d..a624c1d 100644
--- a/Source/WebCore/platform/graphics/android/rendering/TileTexture.h
+++ b/Source/WebCore/platform/graphics/android/rendering/TileTexture.h
@@ -80,7 +80,8 @@ public:
     Color pureColor() { return m_pureColor; }
 
     void drawGL(bool isLayer, const SkRect& rect, float opacity,
-                const TransformationMatrix* transform, bool forceBlending = false);
+                const TransformationMatrix* transform, bool forceBlending = false,
+                bool usePointSampling = false);
 private:
     TextureInfo m_ownTextureInfo;
     SkSize m_size;