OPENGL: Support RGB555 for OpenGL ES output.

This mode should *not* be used by any new engines/code. If someone is going
to use it and says it works with the OpenGL output, please make them wear a
red uniform and beam them onto a remote planet.

4 files changed, 95 insertions, 2 deletions

diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index 78ae27d8a6..8db5f6a934 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -985,6 +985,15 @@ Texture *OpenGLGraphicsManager::createTexture(const Graphics::PixelFormat &forma
 		} else {
 			return new TextureCLUT8(glIntFormat, glFormat, glType, virtFormat);
 		}
+#if !USE_FORCED_GL
+	} else if (isGLESContext() && format == Graphics::PixelFormat(2, 5, 5, 5, 0, 10, 5, 0, 0)) {
+		// OpenGL ES does not support a texture format usable for RGB555.
+		// Since SCUMM uses this pixel format for some games (and there is no
+		// hope for this to change anytime soon) we use pixel format
+		// conversion to a supported texture format. However, this is a one
+		// time exception.
+		return new TextureRGB555();
+#endif // !USE_FORCED_GL
 	} else {
 		const bool supported = getGLPixelFormat(format, glIntFormat, glFormat, glType);
 		if (!supported) {
diff --git a/backends/graphics/opengl/texture.cpp b/backends/graphics/opengl/texture.cpp
index b866b15bfd..fadfd99aaa 100644
--- a/backends/graphics/opengl/texture.cpp
+++ b/backends/graphics/opengl/texture.cpp
@@ -369,4 +369,64 @@ void TextureCLUT8::updateTexture() {
 	Texture::updateTexture();
 }
 
+#if !USE_FORCED_GL
+TextureRGB555::TextureRGB555()
+    : Texture(GL_RGB, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, Graphics::PixelFormat(2, 5, 6, 5, 0, 11, 5, 0, 0)),
+      _rgb555Data() {
+}
+
+TextureRGB555::~TextureRGB555() {
+	_rgb555Data.free();
+}
+
+void TextureRGB555::allocate(uint width, uint height) {
+	Texture::allocate(width, height);
+
+	// We only need to reinitialize our RGB555 surface when the output size
+	// changed.
+	if (width == _rgb555Data.w && height == _rgb555Data.h) {
+		return;
+	}
+
+	_rgb555Data.create(width, height, Graphics::PixelFormat(2, 5, 5, 5, 0, 10, 5, 0, 0));
+}
+
+Graphics::PixelFormat TextureRGB555::getFormat() const {
+	return Graphics::PixelFormat(2, 5, 5, 5, 0, 10, 5, 0, 0);
+}
+
+void TextureRGB555::updateTexture() {
+	if (!isDirty()) {
+		return;
+	}
+
+	// Convert color space.
+	Graphics::Surface *outSurf = Texture::getSurface();
+
+	const Common::Rect dirtyArea = getDirtyArea();
+
+	uint16 *dst = (uint16 *)outSurf->getBasePtr(dirtyArea.left, dirtyArea.top);
+	const uint dstAdd = outSurf->pitch - 2 * dirtyArea.width();
+
+	const uint16 *src = (const uint16 *)_rgb555Data.getBasePtr(dirtyArea.left, dirtyArea.top);
+	const uint srcAdd = _rgb555Data.pitch - 2 * dirtyArea.width();
+
+	for (int height = dirtyArea.height(); height > 0; --height) {
+		for (int width = dirtyArea.width(); width > 0; --width) {
+			const uint16 color = *src++;
+
+			*dst++ =   ((color & 0x7C00) << 1)                             // R
+			         | (((color & 0x03E0) << 1) | ((color & 0x0200) >> 4)) // G
+			         | (color & 0x001F);                                   // B
+		}
+
+		src = (const uint16 *)((const byte *)src + srcAdd);
+		dst = (uint16 *)((byte *)dst + dstAdd);
+	}
+
+	// Do generic handling of updating the texture.
+	Texture::updateTexture();
+}
+#endif // !USE_FORCED_GL
+
 } // End of namespace OpenGL
diff --git a/backends/graphics/opengl/texture.h b/backends/graphics/opengl/texture.h
index ad70833544..4c2126741c 100644
--- a/backends/graphics/opengl/texture.h
+++ b/backends/graphics/opengl/texture.h
@@ -170,6 +170,27 @@ private:
 	byte *_palette;
 };
 
+#if !USE_FORCED_GL
+class TextureRGB555 : public Texture {
+public:
+	TextureRGB555();
+	virtual ~TextureRGB555();
+
+	virtual void allocate(uint width, uint height);
+
+	virtual Graphics::PixelFormat getFormat() const;
+
+	virtual Graphics::Surface *getSurface() { return &_rgb555Data; }
+	virtual const Graphics::Surface *getSurface() const { return &_rgb555Data; }
+
+protected:
+	virtual void updateTexture();
+
+private:
+	Graphics::Surface _rgb555Data;
+};
+#endif // !USE_FORCED_GL
+
 } // End of namespace OpenGL
 
 #endif
diff --git a/backends/graphics/openglsdl/openglsdl-graphics.cpp b/backends/graphics/openglsdl/openglsdl-graphics.cpp
index a945138578..583d54b30b 100644
--- a/backends/graphics/openglsdl/openglsdl-graphics.cpp
+++ b/backends/graphics/openglsdl/openglsdl-graphics.cpp
@@ -221,13 +221,16 @@ Common::List<Graphics::PixelFormat> OpenGLSdlGraphicsManager::getSupportedFormat
 		// ABGR8888
 		formats.push_back(Graphics::PixelFormat(4, 8, 8, 8, 8, 0, 8, 16, 24));
 #endif
-		// RGB555, this is used by SCUMM HE 16 bit games.
-		formats.push_back(Graphics::PixelFormat(2, 5, 5, 5, 0, 10, 5, 0, 0));
 #if !USE_FORCED_GL
 	}
 #endif
 #endif
 
+	// RGB555, this is used by SCUMM HE 16 bit games.
+	// This is not natively supported by OpenGL ES implementations, we convert
+	// the pixel format internally.
+	formats.push_back(Graphics::PixelFormat(2, 5, 5, 5, 0, 10, 5, 0, 0));
+
 	formats.push_back(Graphics::PixelFormat::createFormatCLUT8());
 
 	return formats;