[[ canvas ]] Add begin effect only layer with <effect> on <canvas> syntax

livecodeian · livecodeian · commit 940ad55fc445 · 2019-05-14T11:10:08.000+01:00
This allows drawing shadow &amp; glow effects without rendering the source
diff --git a/docs/lcb/notes/feature-effect_only_layer.md b/docs/lcb/notes/feature-effect_only_layer.md
@@ -0,0 +1,13 @@
+# LiveCode Builder Host Library
+## Canvas library
+
+A new statement `begin effect only layer with <effect>` has been implemented to
+allow drawing shadow & glow effects without rendering the source content
+
+For example to draw a dropshadow of a rectangle without drawing the rectangle itself:
+	variable tEffect as Effect
+	put outer shadow effect into tEffect
+
+	begin effect only layer with tEffect on this canvas
+	fill rectangle path of rectangle [50,50,100,100] on this canvas
+	end layer on this canvas
diff --git a/engine/src/canvas.lcb b/engine/src/canvas.lcb
@@ -4281,6 +4281,7 @@ public foreign handler MCCanvasSaveState(in pCanvas as Canvas) returns nothing b
 public foreign handler MCCanvasRestoreState(in pCanvas as Canvas) returns nothing binds to "<builtin>"
 public foreign handler MCCanvasBeginLayer(in pCanvas as Canvas) returns nothing binds to "<builtin>"
 public foreign handler MCCanvasBeginLayerWithEffect(in pEffect as Effect, in pCanvas as Canvas) returns nothing binds to "<builtin>"
+public foreign handler MCCanvasBeginEffectOnlyLayerWithEffect(in pEffect as Effect, in pCanvas as Canvas) returns nothing binds to "<builtin>"
 public foreign handler MCCanvasEndLayer(in pCanvas as Canvas) returns nothing binds to "<builtin>"
 
 public foreign handler MCCanvasFill(in pCanvas as Canvas) returns nothing binds to "<builtin>"
@@ -4486,6 +4487,11 @@ begin
 	MCCanvasBeginLayer(mCanvas)
 	MCCanvasBeginLayerWithEffect(mEffect, mCanvas)
 end syntax
+syntax CanvasOperationBeginEffectOnlyLayer is statement
+	"begin" "effect" "only" "layer" "with" <mEffect: Expression> "on" <mCanvas: Expression>
+begin
+	MCCanvasBeginEffectOnlyLayerWithEffect(mEffect, mCanvas)
+end syntax
 
 //////////
 
diff --git a/engine/src/module-canvas.cpp b/engine/src/module-canvas.cpp
@@ -5658,8 +5658,21 @@ static void MCPolarCoordsToCartesian(MCGFloat p_distance, MCGFloat p_angle, MCGF
 	r_y = p_distance * sin(p_angle);
 }
 
+void _MCCanvasBeginLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canvas, bool p_isolated);
+
 MC_DLLEXPORT_DEF
 void MCCanvasBeginLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canvas)
+{
+	_MCCanvasBeginLayerWithEffect(p_effect, p_canvas, false);
+}
+
+MC_DLLEXPORT_DEF
+void MCCanvasBeginEffectOnlyLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canvas)
+{
+	_MCCanvasBeginLayerWithEffect(p_effect, p_canvas, true);
+}
+
+void _MCCanvasBeginLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canvas, bool p_isolated)
 {
 	__MCCanvasImpl *t_canvas;
 	t_canvas = MCCanvasGet(p_canvas);
@@ -5676,6 +5689,8 @@ void MCCanvasBeginLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canv
 	MCCanvasFloat t_spread;
 	t_spread = MCClamp(t_effect_impl->spread, 0.0, 1.0);
 	
+	t_effects.isolated = p_isolated;
+	
 	switch (t_effect_impl->type)
 	{
 		case kMCCanvasEffectTypeColorOverlay:
diff --git a/engine/src/module-canvas.h b/engine/src/module-canvas.h
@@ -563,6 +563,7 @@ extern "C" MC_DLLEXPORT void MCCanvasSaveState(MCCanvasRef p_canvas);
 extern "C" MC_DLLEXPORT void MCCanvasRestoreState(MCCanvasRef p_canvas);
 extern "C" MC_DLLEXPORT void MCCanvasBeginLayer(MCCanvasRef p_canvas);
 extern "C" MC_DLLEXPORT void MCCanvasBeginLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canvas);
+extern "C" MC_DLLEXPORT void MCCanvasBeginEffectOnlyLayerWithEffect(MCCanvasEffectRef p_effect, MCCanvasRef p_canvas);
 extern "C" MC_DLLEXPORT void MCCanvasEndLayer(MCCanvasRef p_canvas);
 extern "C" MC_DLLEXPORT void MCCanvasFill(MCCanvasRef p_canvas);
 extern "C" MC_DLLEXPORT void MCCanvasFillPath(MCCanvasPathRef p_path, MCCanvasRef p_canvas);
