api: revise the gl target() api.

API modification:
- Result GlCanvas::target(int32_t id, uint32_t w, uint32_t h)
 -> Result GlCanvas::target(int32_t id, uint32_t w, uint32_t h, ColorSpace cs)
- Tvg_Result tvg_glcanvas_set_target(Tvg_Canvas* canvas, int32_t id, uint32_t w, uint32_t h)
 -> Tvg_Result tvg_glcanvas_set_target(Tvg_Canvas* canvas, int32_t id, uint32_t w, uint32_t h, Tvg_Colorspace cs)

issue: https://github.com/thorvg/thorvg/issues/1372

examples/Example.h

@@ -344,7 +344,7 @@ struct GlWindow : Window
     void resize() override
     {
         //Set the canvas target and draw on it.
-        verify(static_cast<tvg::GlCanvas*>(canvas)->target(0, width, height));
+        verify(static_cast<tvg::GlCanvas*>(canvas)->target(0, width, height, tvg::ColorSpace::ABGR8888S));
     }
 
     void refresh() override

examples/MultiCanvas.cpp

@@ -218,7 +218,7 @@ void runGl()
         auto canvas = unique_ptr<tvg::GlCanvas>(tvg::GlCanvas::gen());
 
         // Pass the framebuffer id to the GlCanvas
-        tvgexam::verify(canvas->target(glFbo.fbo, SIZE, SIZE));
+        tvgexam::verify(canvas->target(glFbo.fbo, SIZE, SIZE, tvg::ColorSpace::ABGR8888S));
 
         content(canvas.get());
         if (tvgexam::verify(canvas->draw())) {

inc/thorvg.h

@@ -1732,6 +1732,7 @@ public:
      * @param[in] id The GL target ID, usually indicating the FBO ID. A value of @c 0 specifies the main surface.
      * @param[in] w The width (in pixels) of the raster image.
      * @param[in] h The height (in pixels) of the raster image.
+     * @param[in] cs Specifies how the pixel values should be interpreted. Currently, it only allows @c ColorSpace::ABGR8888S as @c GL_RGBA8.
      *
      * @retval Result::InsufficientCondition if the canvas is performing rendering. Please ensure the canvas is synced.
      * @retval Result::NonSupport In case the gl engine is not supported.
@@ -1739,10 +1740,9 @@ public:
      * @see Canvas::viewport()
      * @see Canvas::sync()
      *
-     * @note Currently, this only allows the GL_RGBA8 color space format.
      * @note Experimental API
     */
-    Result target(int32_t id, uint32_t w, uint32_t h) noexcept;
+    Result target(int32_t id, uint32_t w, uint32_t h, ColorSpace cs) noexcept;
 
     /**
      * @brief Creates a new GlCanvas object.

src/bindings/capi/thorvg_capi.h

@@ -522,15 +522,15 @@ TVG_API Tvg_Canvas* tvg_glcanvas_create(void);
 * \param[in] id The GL target ID, usually indicating the FBO ID. A value of @c 0 specifies the main surface.
 * \param[in] w The width (in pixels) of the raster image.
 * \param[in] h The height (in pixels) of the raster image.
+* \param[in] cs Specifies how the pixel values should be interpreted. Currently, it only allows @c TVG_COLORSPACE_ABGR8888S as @c GL_RGBA8.
 *
 * \return Tvg_Result enumeration.
 * \retval TVG_RESULT_INSUFFICIENT_CONDITION if the canvas is performing rendering. Please ensure the canvas is synced.
 * \retval TVG_RESULT_NOT_SUPPORTED In case the gl engine is not supported.
 *
-* \note Currently, this only allows the GL_RGBA8 color space format.
 * \note Experimental API
 */
-TVG_API Tvg_Result tvg_glcanvas_set_target(Tvg_Canvas* canvas, int32_t id, uint32_t w, uint32_t h);
+TVG_API Tvg_Result tvg_glcanvas_set_target(Tvg_Canvas* canvas, int32_t id, uint32_t w, uint32_t h, Tvg_Colorspace cs);
 
 /** \} */   // end defgroup ThorVGCapi_GlCanvas
 

src/bindings/capi/tvgCapi.cpp

@@ -102,10 +102,10 @@ TVG_API Tvg_Result tvg_swcanvas_set_target(Tvg_Canvas* canvas, uint32_t* buffer,
 }
 
 
-TVG_API Tvg_Result tvg_glcanvas_set_target(Tvg_Canvas* canvas, int32_t id, uint32_t w, uint32_t h)
+TVG_API Tvg_Result tvg_glcanvas_set_target(Tvg_Canvas* canvas, int32_t id, uint32_t w, uint32_t h, Tvg_Colorspace cs)
 {
     if (!canvas) return TVG_RESULT_INVALID_ARGUMENT;
-    return (Tvg_Result) reinterpret_cast<GlCanvas*>(canvas)->target(id, w, h);
+    return (Tvg_Result) reinterpret_cast<GlCanvas*>(canvas)->target(id, w, h, static_cast<ColorSpace>(cs));
 }
 
 

src/renderer/tvgGlCanvas.cpp

@@ -59,9 +59,11 @@ GlCanvas::~GlCanvas()
 }
 
 
-Result GlCanvas::target(int32_t id, uint32_t w, uint32_t h) noexcept
+Result GlCanvas::target(int32_t id, uint32_t w, uint32_t h, ColorSpace cs) noexcept
 {
 #ifdef THORVG_GL_RASTER_SUPPORT
+    if (cs != ColorSpace::ABGR8888S) return Result::NonSupport;
+
     if (Canvas::pImpl->status != Status::Damaged && Canvas::pImpl->status != Status::Synced) {
         return Result::InsufficientCondition;
     }