GUI: Fix hard shadow under HiDPI rendering (#4908)

graphics/VectorRenderer.cpp

@@ -52,6 +52,7 @@ void VectorRenderer::drawStep(const Common::Rect &area, const Common::Rect &clip
 	setStrokeWidth(step.stroke);
 	setFillMode((FillMode)step.fillMode);
 	setClippingRect(applyStepClippingRect(area, clip, step));
+	setShadowIntensity(step.shadowIntensity);
 
 	_dynamicData = extra;
 

graphics/VectorRenderer.h

@@ -92,6 +92,8 @@ struct DrawStep {
 
 	uint32 scale; /**< scale of all the coordinates in FIXED POINT with 16 bits mantissa */
 
+	uint32 shadowIntensity; /**< interval for drawing shadows in FIXED POINT with 16 bits mantissa */
+
 	GUI::ThemeEngine::AutoScaleMode autoscale; /**< scale alphaimage if present */
 
 	DrawStep() {
@@ -107,6 +109,7 @@ struct DrawStep {
 		shadowFillMode = 0;
 		extraData = 0;
 		scale = 0;
+		shadowIntensity = 1 << 16;
 		autoscale = GUI::ThemeEngine::kAutoScaleNone;
 	}
 };
@@ -375,6 +378,18 @@ public:
 			_gradientFactor = factor;
 	}
 
+	/**
+	 * Sets the pixel interval for drawing shadows
+	 * 
+	 * @param shadowIntensity interval for drawing shadows
+	 */
+	virtual void setShadowIntensity(uint32 shadowIntensity) {
+		if (shadowIntensity > 0)
+			_shadowIntensity = shadowIntensity;
+		else
+			warning("setShadowIntensity(): zero intensity");
+	}
+
 	/**
 	 * Sets the clipping rectangle to be used by draw calls.
 	 *
@@ -544,6 +559,7 @@ protected:
 	uint32 _dynamicData; /**< Dynamic data from the GUI Theme that modifies the drawing of the current shape */
 
 	int _gradientFactor; /**< Multiplication factor of the active gradient */
+	uint32 _shadowIntensity; /**< Intensity of the shadow */
 };
 /** @} */
 } // End of namespace Graphics

graphics/VectorRendererSpec.cpp

@@ -1286,9 +1286,9 @@ drawRoundedSquare(int x, int y, int r, int w, int h) {
 		&& y + h + Base::_shadowOffset + 1 < Base::_activeSurface->h
 		&& h > (Base::_shadowOffset + 1) * 2) {
 		if (useOriginal) {
-			drawRoundedSquareShadow(x, y, r, w, h, Base::_shadowOffset);
+			drawRoundedSquareShadow(x, y, r, w, h, Base::_shadowOffset, Base::_shadowIntensity);
 		} else {
-			drawRoundedSquareShadowClip(x, y, r, w, h, Base::_shadowOffset);
+			drawRoundedSquareShadowClip(x, y, r, w, h, Base::_shadowOffset, Base::_shadowIntensity);
 		}
 	}
 
@@ -3666,7 +3666,7 @@ drawSquareShadowClip(int x, int y, int w, int h, int offset) {
 
 template<typename PixelType>
 void VectorRendererSpec<PixelType>::
-drawRoundedSquareShadow(int x1, int y1, int r, int w, int h, int offset) {
+drawRoundedSquareShadow(int x1, int y1, int r, int w, int h, int offset, uint32 shadowIntensity) {
 	int pitch = _activeSurface->pitch / _activeSurface->format.bytesPerPixel;
 
 	// "Harder" shadows when having lower BPP, since we will have artifacts (greenish tint on the modern theme)
@@ -3686,7 +3686,9 @@ drawRoundedSquareShadow(int x1, int y1, int r, int w, int h, int offset) {
 
 	// Soft shadows are constructed by drawing increasingly
 	// darker and smaller rectangles on top of each other.
-	for (int i = offset; i >= 0; i--) {
+	uint32 targetOffset = (uint32)offset << 16;
+	int curOffset = 0;
+	for (uint32 i = shadowIntensity; i <= targetOffset; i += shadowIntensity) {
 		int f, ddF_x, ddF_y;
 		int x, y, px, py;
 
@@ -3747,7 +3749,8 @@ drawRoundedSquareShadow(int x1, int y1, int r, int w, int h, int offset) {
 		}
 
 		// Make shadow smaller each iteration
-		shadowRect.grow(-1);
+		shadowRect.grow(curOffset - (i >> 16));
+		curOffset = i >> 16;
 
 		if (_shadowFillMode == kShadowExponential)
 			// Multiply with expfactor
@@ -3757,7 +3760,7 @@ drawRoundedSquareShadow(int x1, int y1, int r, int w, int h, int offset) {
 
 template<typename PixelType>
 void VectorRendererSpec<PixelType>::
-drawRoundedSquareShadowClip(int x1, int y1, int r, int w, int h, int offset) {
+drawRoundedSquareShadowClip(int x1, int y1, int r, int w, int h, int offset, uint32 shadowIntensity) {
 	int pitch = _activeSurface->pitch / _activeSurface->format.bytesPerPixel;
 
 	// "Harder" shadows when having lower BPP, since we will have artifacts (greenish tint on the modern theme)
@@ -3777,7 +3780,13 @@ drawRoundedSquareShadowClip(int x1, int y1, int r, int w, int h, int offset) {
 
 	// Soft shadows are constructed by drawing increasingly
 	// darker and smaller rectangles on top of each other.
-	for (int i = offset; i >= 0; i--) {
+
+	// HACK: shadowIntensity is tailed with 16-bits mantissa. We also represent the
+	// offset as a 16.16 fixed point number here as termination condition to simplify
+	// looping logic.
+	uint32 targetOffset = (uint32)offset << 16;
+	int curOffset = 0;
+	for (uint32 i = shadowIntensity; i <= targetOffset; i += shadowIntensity) {
 		int f, ddF_x, ddF_y;
 		int x, y, px, py;
 
@@ -3840,7 +3849,8 @@ drawRoundedSquareShadowClip(int x1, int y1, int r, int w, int h, int offset) {
 		}
 
 		// Make shadow smaller each iteration
-		shadowRect.grow(-1);
+		shadowRect.grow(curOffset - (i >> 16));
+		curOffset = i >> 16;
 
 		if (_shadowFillMode == kShadowExponential)
 			// Multiply with expfactor

graphics/VectorRendererSpec.h

@@ -258,8 +258,8 @@ protected:
 	 */
 	virtual void drawSquareShadow(int x, int y, int w, int h, int offset);
 	virtual void drawSquareShadowClip(int x, int y, int w, int h, int offset);
-	virtual void drawRoundedSquareShadow(int x, int y, int r, int w, int h, int offset);
+	virtual void drawRoundedSquareShadow(int x, int y, int r, int w, int h, int offset, uint32 shadowIntensity);
-	virtual void drawRoundedSquareShadowClip(int x, int y, int r, int w, int h, int offset);
+	virtual void drawRoundedSquareShadowClip(int x, int y, int r, int w, int h, int offset, uint32 shadowIntensity);
 
 	/**
 	 * Calculates the color gradient on a given point.
@@ -380,8 +380,8 @@ protected:
 
 	virtual void drawInteriorRoundedSquareAlg(int x1, int y1, int r, int w, int h, PixelType color, VectorRenderer::FillMode fill_m);
 
-	virtual void drawRoundedSquareShadow(int x, int y, int r, int w, int h, int offset) {
+	virtual void drawRoundedSquareShadow(int x, int y, int r, int w, int h, int offset, uint32 shadowIntensity) {
-		Base::drawRoundedSquareShadow(x, y, r, w, h, offset);
+		Base::drawRoundedSquareShadow(x, y, r, w, h, offset, shadowIntensity);
 	}
 
 	virtual void drawTabAlg(int x, int y, int w, int h, int r,

gui/ThemeParser.cpp

@@ -161,6 +161,7 @@ Graphics::DrawStep *ThemeParser::defaultDrawStep() {
 	step->fillMode = Graphics::VectorRenderer::kFillDisabled;
 	step->scale = (1 << 16);
 	step->radius = 0xFF;
+	step->shadowIntensity = SCALEVALUE((1 << 16));
 
 	return step;
 }