cc: Add point-based UV coordinate on TextureLayer

cc/texture_draw_quad.cc

Index: cc/texture_draw_quad.cc
diff --git a/cc/texture_draw_quad.cc b/cc/texture_draw_quad.cc
index adce50fb648676c5c6c4637da6b047e79e3e2092..a921eaa95f1b40702a65e6c67bb4ee8ada4257f2 100644
--- a/cc/texture_draw_quad.cc
+++ b/cc/texture_draw_quad.cc
@@ -21,7 +21,8 @@ scoped_ptr<TextureDrawQuad> TextureDrawQuad::Create() {
 void TextureDrawQuad::SetNew(const SharedQuadState* shared_quad_state,
                              gfx::Rect rect, gfx::Rect opaque_rect,
                              unsigned resource_id, bool premultiplied_alpha,
-                             const gfx::RectF& uv_rect,
+                             const gfx::PointF& uv_top_left,
+                             const gfx::PointF& uv_bottom_right,
                              const float vertex_opacity[4], bool flipped) {
   gfx::Rect visible_rect = rect;
   bool needs_blending = vertex_opacity[0] != 1.0f || vertex_opacity[1] != 1.0f
@@ -30,7 +31,8 @@ void TextureDrawQuad::SetNew(const SharedQuadState* shared_quad_state,
                    opaque_rect, visible_rect, needs_blending);
   this->resource_id = resource_id;
   this->premultiplied_alpha = premultiplied_alpha;
-  this->uv_rect = uv_rect;
+  this->uv_top_left = uv_top_left;
+  this->uv_bottom_right = uv_bottom_right;
   this->vertex_opacity[0] = vertex_opacity[0];
   this->vertex_opacity[1] = vertex_opacity[1];
   this->vertex_opacity[2] = vertex_opacity[2];
@@ -42,13 +44,15 @@ void TextureDrawQuad::SetAll(const SharedQuadState* shared_quad_state,
                              gfx::Rect rect, gfx::Rect opaque_rect,
                              gfx::Rect visible_rect, bool needs_blending,
                              unsigned resource_id, bool premultiplied_alpha,
-                             const gfx::RectF& uv_rect,
+                             const gfx::PointF& uv_top_left,
+                             const gfx::PointF& uv_bottom_right,
                              const float vertex_opacity[4], bool flipped) {
   DrawQuad::SetAll(shared_quad_state, DrawQuad::TEXTURE_CONTENT, rect,
                    opaque_rect, visible_rect, needs_blending);
   this->resource_id = resource_id;
   this->premultiplied_alpha = premultiplied_alpha;
-  this->uv_rect = uv_rect;
+  this->uv_top_left = uv_top_left;
+  this->uv_bottom_right = uv_bottom_right;
   this->vertex_opacity[0] = vertex_opacity[0];
   this->vertex_opacity[1] = vertex_opacity[1];
   this->vertex_opacity[2] = vertex_opacity[2];
@@ -86,18 +90,20 @@ bool TextureDrawQuad::PerformClipping() {
   gfx::RectF clippedRect = IntersectRects(rectF, clipRect());
   if (clippedRect.IsEmpty()) {
     rect = gfx::Rect();
-    uv_rect = gfx::RectF();
+    uv_top_left = gfx::PointF();
+    uv_bottom_right = gfx::PointF();

[danakj, 2013/01/11 02:21:51]

should this be PointF(1.f, 1.f)

[Jerome, 2013/01/11 18:00:01]

To keep the previous behavior uv_bottom_right should be 0,0 too.

     return true;
   }
 
   // Create a new uv-rect by clipping the old one to the new bounds.
-  uv_rect = gfx::RectF(
-      uv_rect.x()
-          + uv_rect.width() / rectF.width() * (clippedRect.x() - rectF.x()),
-      uv_rect.y()
-          + uv_rect.height() / rectF.height() * (clippedRect.y() - rectF.y()),
-      uv_rect.width() / rectF.width() * clippedRect.width(),
-      uv_rect.height() / rectF.height() * clippedRect.height());
+  float u_scale = (uv_bottom_right.x() - uv_top_left.x()) / rectF.width();

[danakj, 2013/01/11 02:21:51]

I might have messed this up, or you might see a more clean/more semantically
descriptive way to do this, but generally it's nice if we can write the math in
terms of points/vectors instead of breaking it down into components. So I was
thinking something like:

gfx::PointF old_top_left = uv_top_left;
gfx::PointF old_bottom_left = uv_bottom_left;

gfx::Vector2dF clipped_rect_offset = clippedRect.origin() - rectF.origin();

uv_top_left = old_top_left +
    gfx::ScaleVector2dF(
        old_bottom_right - old_top_left,
        clipped_rect_offset.x() / rectF.width(),
        clipped_rect_offset.y() / rectF.height());
uv_bottom_right = uv_top_left +
    gfx::ScaleVector2dF(
        old_bottom_right - old_top_left,
        clippedRect.width() / rectF.width(),
        clippedRect.height() / rectF.height());

WDYT?

[Jerome, 2013/01/11 18:00:01]

LGTM.
Any reason why there is no 
void Vector2dF::Scale(const Vector2dF& other)? That would allow to keep almost
everything vectors.

[danakj, 2013/01/11 20:00:12]

Ya, I thought about this too.. Ill file a bug

+  float v_scale = (uv_bottom_right.y() - uv_top_left.y()) / rectF.height();
+  uv_bottom_right = gfx::PointF(
+      uv_top_left.x() + u_scale * (clippedRect.right() - rectF.x()),
+      uv_top_left.y() + v_scale * (clippedRect.bottom() - rectF.y()));
+  uv_top_left = gfx::PointF(
+      uv_top_left.x() + u_scale * (clippedRect.x() - rectF.x()),
+      uv_top_left.y() + v_scale * (clippedRect.y() - rectF.y()));
 
   // Indexing according to the quad vertex generation:
   // 1--2