* Add Style::HasTransparency() which just tells if any of the colors that the

style uses has an alpha value below 255.
* Add support for intermediate rendering passes to IconRenderer. Normally,
  the whole icon is rendered in a single pass, which means shapes cannot
  overlap. With the change, intermediate rendering passes are inserted when
  a shape is encountered that contains transparency. This is an easy way to
  allow for more feature rich icons, with easy support for glossy/reflective
  surface effects or other such effects that require support for transparent
  shapes on top of other shapes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24490 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/libs/icon/IconRenderer.cpp

@@ -26,7 +26,7 @@
 
 using std::nothrow;
 
-class StyleHandler {
+class IconRenderer::StyleHandler {
 	struct StyleItem {
 		Style*			style;
 		Transformation	transformation;
@@ -96,7 +96,7 @@ private:
 
 // color
 const agg::rgba8&
-StyleHandler::color(unsigned styleIndex)
+IconRenderer::StyleHandler::color(unsigned styleIndex)
 {
 	StyleItem* styleItem = (StyleItem*)fStyles.ItemAt(styleIndex);
 	if (!styleItem) {
@@ -115,8 +115,8 @@ StyleHandler::color(unsigned styleIndex)
 
 // generate_span
 void
-StyleHandler::generate_span(agg::rgba8* span, int x, int y,
-							unsigned len, unsigned styleIndex)
+IconRenderer::StyleHandler::generate_span(agg::rgba8* span, int x, int y,
+	unsigned len, unsigned styleIndex)
 {
 	StyleItem* styleItem = (StyleItem*)fStyles.ItemAt(styleIndex);
 	if (!styleItem || !styleItem->style->Gradient()) {
@@ -172,12 +172,9 @@ StyleHandler::generate_span(agg::rgba8* span, int x, int y,
 // _GenerateGradient
 template<class GradientFunction>
 void
-StyleHandler::_GenerateGradient(agg::rgba8* span, int x, int y, unsigned len,
-								GradientFunction function,
-								int32 start, int32 end,
-								const agg::rgba8* gradientColors,
-								Transformation& gradientTransform)
-
+IconRenderer::StyleHandler::_GenerateGradient(agg::rgba8* span, int x, int y,
+	unsigned len, GradientFunction function, int32 start, int32 end,
+	const agg::rgba8* gradientColors, Transformation& gradientTransform)
 {
 	typedef agg::pod_auto_array<agg::rgba8, 256>	ColorArray;
 	typedef agg::span_interpolator_linear<>			Interpolator;
@@ -393,6 +390,12 @@ IconRenderer::_Render(const BRect& r)
 			printf("IconRenderer::_Render() - out of memory\n");
 			break;
 		}
+
+		// if this is not the first shape, and the style contains
+		// transparency, commit a render pass of previous shapes
+		if (i > 0 && style->HasTransparency())
+			_CommitRenderPass(styleHandler);
+
 		fRasterizer.styles(styleIndex, -1);
 		styleIndex++;
 
@@ -409,12 +412,7 @@ IconRenderer::_Render(const BRect& r)
 		}
 	}
 
-	agg::render_scanlines_compound(fRasterizer,
-								   fScanline,
-								   fBinaryScanline,
-								   fBaseRendererPre,
-								   fSpanAllocator,
-								   styleHandler);
+	_CommitRenderPass(styleHandler, false);
 
 	if (fGammaTable.gamma() != 1.0)
 		fPixelFormat.apply_gamma_inv(fGammaTable);
@@ -423,6 +421,19 @@ IconRenderer::_Render(const BRect& r)
 //printf("rendering 64x64: %lld\n", system_time() - start);
 }
 
+// _CommitRenderPass
+void
+IconRenderer::_CommitRenderPass(StyleHandler& styleHandler, bool reset)
+{
+	agg::render_scanlines_compound(fRasterizer,
+								   fScanline,
+								   fBinaryScanline,
+								   fBaseRendererPre,
+								   fSpanAllocator,
+								   styleHandler);
+	if (reset)
+		fRasterizer.reset();
+}
 
 
 

src/libs/icon/IconRenderer.h

@@ -72,7 +72,11 @@ class IconRenderer {
 			void				Demultiply();
 
  private:
+		class StyleHandler;
+
 			void				_Render(const BRect& area);
+			void				_CommitRenderPass(StyleHandler& styleHandler,
+									bool reset = true);
 
 			BBitmap*			fBitmap;
 			const BBitmap*		fBackground;

src/libs/icon/style/Style.cpp

@@ -162,6 +162,22 @@ Style::operator==(const Style& other) const
 
 #endif // ICON_O_MATIC
 
+// HasTransparency
+bool
+Style::HasTransparency() const
+{
+	if (fGradient) {
+		int32 count = fGradient->CountColors();
+		for (int32 i = 0; i < count; i++) {
+			color_step* step = fGradient->ColorAtFast(i);
+			if (step->color.alpha < 255)
+				return true;
+		}
+		return false;
+	}
+	return fColor.alpha < 255;
+}
+
 // SetColor
 void
 Style::SetColor(const rgb_color& color)

src/libs/icon/style/Style.h

@@ -55,6 +55,8 @@ class Style {
 	inline	void				Notify() {}
 #endif // ICON_O_MATIC
 
+			bool				HasTransparency() const;
+
 			void				SetColor(const rgb_color& color);
 	inline	rgb_color			Color() const
 									{ return fColor; }