[[ Bug 12557 ]] Force the use of anti-aliasing when the context has a non-integer transform

livecodeian · runrevmark · commit 27b268512431 · 2014-06-19T17:27:18.000+01:00
diff --git a/engine/src/graphicscontext.cpp b/engine/src/graphicscontext.cpp
@@ -124,6 +124,23 @@ static MCGPathRef MCGPathFromMCPath(MCPath *p_path)
 
 ////////////////////////////////////////////////////////////////////////////////
 
+bool MCGFloatIsInteger(MCGFloat p_float)
+{
+	return floorf(p_float) == p_float;
+}
+
+bool MCGAffineTransformIsInteger(const MCGAffineTransform &p_transform)
+{
+	return MCGFloatIsInteger(p_transform.a) &&
+		MCGFloatIsInteger(p_transform.b) &&
+		MCGFloatIsInteger(p_transform.c) &&
+		MCGFloatIsInteger(p_transform.d) &&
+		MCGFloatIsInteger(p_transform.tx) &&
+		MCGFloatIsInteger(p_transform.ty);
+}
+
+//////////
+
 void MCGraphicsContext::init(MCGContextRef p_context)
 {
 	m_gcontext = MCGContextRetain(p_context);
@@ -142,6 +159,11 @@ void MCGraphicsContext::init(MCGContextRef p_context)
 	m_dash_lengths = nil;
 	m_dash_count = 0;
 	
+	// IM-2014-06-19: [[ Bug 12557 ]] Force antialiasing if the underlying context has a non-integer transform set
+	m_force_antialiasing = !MCGAffineTransformIsInteger(MCGContextGetDeviceTransform(p_context));
+	if (m_force_antialiasing)
+		MCGContextSetShouldAntialias(p_context, true);
+
 	MCGContextSetFlatness(p_context, 1 / 16.0f);
 }
 
@@ -317,7 +339,8 @@ void MCGraphicsContext::clearorigin(void)
 
 void MCGraphicsContext::setquality(uint1 p_quality)
 {
-	MCGContextSetShouldAntialias(m_gcontext, p_quality == QUALITY_SMOOTH);
+	if (!m_force_antialiasing)
+		MCGContextSetShouldAntialias(m_gcontext, p_quality == QUALITY_SMOOTH);
 }
 
 void MCGraphicsContext::setfunction(uint1 p_function)
diff --git a/engine/src/graphicscontext.h b/engine/src/graphicscontext.h
@@ -113,6 +113,9 @@ class MCGraphicsContext : public MCContext
 	MCGFloat m_dash_phase;
 	MCGFloat *m_dash_lengths;
 	uint32_t m_dash_count;
+
+	// IM-2014-06-19: [[ Bug 12557 ]] Override for the antialias setting
+	bool m_force_antialiasing;
 };
 
 // MW-2014-01-07: [[ Bug 11632 ]] The player object distinguishes between 'screen' and 'offscreen' - in the
diff --git a/libgraphics/src/context.cpp b/libgraphics/src/context.cpp
@@ -2386,10 +2386,46 @@ static bool MCGContextDrawSkBitmap(MCGContextRef self, const SkBitmap &p_bitmap,
 	{
 		// MM-2014-03-12: [[ Bug 11892 ]] If we are not transforming the image, there's no need to apply any filtering.
 		//  Was causing issues in Skia with non null blend modes.
-		SkMatrix::TypeMask t_transform_type;
-		t_transform_type = self -> layer -> canvas -> getTotalMatrix() . getType();
-		if ((t_transform_type == SkMatrix::kIdentity_Mask || t_transform_type == SkMatrix::kTranslate_Mask) &&
-			p_bitmap . width() == p_dst . size . width && p_bitmap . height() == p_dst . size . height)
+
+		// IM-2014-06-19: [[ Bug 12557 ]] More rigourous check to see if we need a filter - Skia will complain if a filter
+		// is used for translation-only transforms or scaling transforms close to the identity.
+		SkMatrix t_matrix;
+		t_matrix = self->layer->canvas->getTotalMatrix();
+
+		MCGRectangle t_tmp_src;
+		MCGFloat t_src_width, t_src_height;
+		if (p_src != nil)
+			t_tmp_src = *p_src;
+		else
+			t_tmp_src = MCGRectangleMake(0, 0, p_bitmap.width(), p_bitmap.height());
+
+		// preconcat the current transform with the transformation from source -> dest rect to obtain the total transformation.
+		SkMatrix t_rect_to_rect;
+		t_rect_to_rect.setRectToRect(MCGRectangleToSkRect(t_tmp_src), MCGRectangleToSkRect(p_dst), SkMatrix::kFill_ScaleToFit);
+
+		t_matrix.preConcat(t_rect_to_rect);
+
+		bool t_no_filter = false;
+
+		// Translation only - no filter
+		if ((t_matrix.getType() & ~SkMatrix::kTranslate_Mask) == 0)
+			t_no_filter = true;
+		else if ((t_matrix.getType() & ~(SkMatrix::kTranslate_Mask | SkMatrix::kScale_Mask)) == 0)
+		{
+			// Translate and scale - if the transformed & rounded destination is the same size as the source then don't filter
+			SkRect src, dst;
+			src.setXYWH(t_tmp_src.origin.x, t_tmp_src.origin.y, t_tmp_src.size.width, t_tmp_src.size.height);
+
+			t_matrix.mapPoints(SkTCast<SkPoint*>(&dst),
+				SkTCast<const SkPoint*>(&src),
+				2);
+
+			SkIRect idst;
+			dst.round(&idst);
+			t_no_filter = idst.width() == t_tmp_src.size.width && idst.height() == t_tmp_src.size.height;
+		}
+
+		if (t_no_filter)
 		{
 			t_paint . setAntiAlias(false);
 			t_paint . setFilterLevel(SkPaint::kNone_FilterLevel);
