[core] add state tracking to pixel store packing alignment

src/mbgl/gl/context.cpp

@@ -283,6 +283,8 @@ void Context::setDirtyState() {
     pointSize.setDirty();
     pixelZoom.setDirty();
     rasterPos.setDirty();
+    pixelStorePack.setDirty();
+    pixelStoreUnpack.setDirty();
 #endif // MBGL_USE_GLES2
     for (auto& tex : texture) {
        tex.setDirty();

src/mbgl/gl/context.hpp

@@ -130,6 +130,8 @@ public:
 #if not MBGL_USE_GLES2
     State<value::PixelZoom> pixelZoom;
     State<value::RasterPos> rasterPos;
+    State<value::PixelStorePack> pixelStorePack;
+    State<value::PixelStoreUnpack> pixelStoreUnpack;
 #endif // MBGL_USE_GLES2
 
 private:

src/mbgl/gl/types.hpp

@@ -62,5 +62,17 @@ enum class PrimitiveType {
     TriangleFan = 0x0006
 };
 
+#if not MBGL_USE_GLES2
+
+struct PixelStorageType {
+    int32_t alignment;
+};
+
+constexpr bool operator!=(const PixelStorageType& a, const PixelStorageType& b) {
+    return a.alignment != b.alignment;
+}
+
+#endif // MBGL_USE_GLES2
+
 } // namespace gl
 } // namespace mbgl

src/mbgl/gl/value.cpp

@@ -389,8 +389,35 @@ RasterPos::Type RasterPos::Get() {
     return { pos[0], pos[1], pos[2], pos[3] };
 }
 
-#endif // MBGL_USE_GLES2
+const constexpr PixelStorePack::Type PixelStorePack::Default;
 
+void PixelStorePack::Set(const Type& value) {
+    assert(value.alignment == 1 || value.alignment == 2 || value.alignment == 4 ||
+           value.alignment == 8);
+    MBGL_CHECK_ERROR(glPixelStorei(GL_PACK_ALIGNMENT, value.alignment));
+}
+
+PixelStorePack::Type PixelStorePack::Get() {
+    Type value;
+    MBGL_CHECK_ERROR(glGetIntegerv(GL_PACK_ALIGNMENT, &value.alignment));
+    return value;
+}
+
+const constexpr PixelStoreUnpack::Type PixelStoreUnpack::Default;
+
+void PixelStoreUnpack::Set(const Type& value) {
+    assert(value.alignment == 1 || value.alignment == 2 || value.alignment == 4 ||
+           value.alignment == 8);
+    MBGL_CHECK_ERROR(glPixelStorei(GL_UNPACK_ALIGNMENT, value.alignment));
+}
+
+PixelStoreUnpack::Type PixelStoreUnpack::Get() {
+    Type value;
+    MBGL_CHECK_ERROR(glGetIntegerv(GL_UNPACK_ALIGNMENT, &value.alignment));
+    return value;
+}
+
+#endif // MBGL_USE_GLES2
 
 } // namespace value
 } // namespace gl

src/mbgl/gl/value.hpp

@@ -259,7 +259,7 @@ struct RasterPos {
         double z;
         double w;
     };
-    static const constexpr Type Default = { 0, 0, 0, 0 };
+    static const constexpr Type Default = { 0, 0, 0, 1 };
     static void Set(const Type&);
     static Type Get();
 };
@@ -268,6 +268,20 @@ constexpr bool operator!=(const RasterPos::Type& a, const RasterPos::Type& b) {
     return a.x != b.x || a.y != b.y || a.z != b.z || a.w != b.w;
 }
 
+struct PixelStorePack {
+    using Type = PixelStorageType;
+    static const constexpr Type Default = { 4 };
+    static void Set(const Type&);
+    static Type Get();
+};
+
+struct PixelStoreUnpack {
+    using Type = PixelStorageType;
+    static const constexpr Type Default = { 4 };
+    static void Set(const Type&);
+    static Type Get();
+};
+
 #endif // MBGL_USE_GLES2
 
 } // namespace value

src/mbgl/renderer/painter_debug.cpp

@@ -68,12 +68,10 @@ void Painter::renderClipMasks(PaintParameters&) {
     context.program = 0;
 
 #if not MBGL_USE_GLES2
-    context.pixelZoom = { 1, 1 };
-    context.rasterPos = { -1, -1, 0, 0 };
 
     // When reading data from the framebuffer, make sure that we are storing the depth values
     // tightly packed into the buffer to avoid buffer overruns. Also see unpacking adjustment below.
-    MBGL_CHECK_ERROR(glPixelStorei(GL_PACK_ALIGNMENT, 1));
+    context.pixelStorePack = { 1 };
 
     // Read the stencil buffer
     const auto viewport = context.viewport.getCurrentValue();
@@ -96,8 +94,9 @@ void Painter::renderClipMasks(PaintParameters&) {
         *it *= factor;
     }
 
-    MBGL_CHECK_ERROR(glPixelStorei(GL_UNPACK_ALIGNMENT, 1));
-    MBGL_CHECK_ERROR(glWindowPos2i(viewport.x, viewport.y));
+    context.pixelZoom = { 1, 1 };
+    context.rasterPos = { -1, -1, 0, 1 };
+    context.pixelStoreUnpack = { 1 };
     MBGL_CHECK_ERROR(glDrawPixels(viewport.size.width, viewport.size.height, GL_LUMINANCE,
                                   GL_UNSIGNED_BYTE, pixels.get()));
 #endif // MBGL_USE_GLES2
@@ -110,12 +109,10 @@ void Painter::renderDepthBuffer(PaintParameters&) {
     context.program = 0;
 
 #if not MBGL_USE_GLES2
-    context.pixelZoom = { 1, 1 };
-    context.rasterPos = { -1, -1, 0, 0 };
 
     // When reading data from the framebuffer, make sure that we are storing the depth values
     // tightly packed into the buffer to avoid buffer overruns. Also see unpacking adjustment below.
-    MBGL_CHECK_ERROR(glPixelStorei(GL_PACK_ALIGNMENT, 1));
+    context.pixelStorePack = { 1 };
 
     // Scales the values in the depth buffer so that they cover the entire grayscale range. This
     // makes it easier to spot tiny differences.
@@ -137,8 +134,9 @@ void Painter::renderDepthBuffer(PaintParameters&) {
                 pixels.get()          // GLvoid * data
                 ));
 
-    MBGL_CHECK_ERROR(glPixelStorei(GL_UNPACK_ALIGNMENT, 1));
-    MBGL_CHECK_ERROR(glWindowPos2i(viewport.x, viewport.y));
+    context.pixelZoom = { 1, 1 };
+    context.rasterPos = { -1, -1, 0, 1 };
+    context.pixelStoreUnpack = { 1 };
     MBGL_CHECK_ERROR(glDrawPixels(viewport.size.width, viewport.size.height, GL_LUMINANCE,
                                   GL_UNSIGNED_BYTE, pixels.get()));
 #endif // MBGL_USE_GLES2