diff options
| -rw-r--r-- | FL/Fl_Graphics_Driver.H | 40 |
1 files changed, 26 insertions, 14 deletions
diff --git a/FL/Fl_Graphics_Driver.H b/FL/Fl_Graphics_Driver.H index b1ec64c07..3cee4763b 100644 --- a/FL/Fl_Graphics_Driver.H +++ b/FL/Fl_Graphics_Driver.H @@ -95,25 +95,37 @@ class FL_EXPORT Fl_Graphics_Driver { friend FL_EXPORT void fl_delete_bitmask(Fl_Bitmask); private: /* ============== Implementation note about image drawing ========================= - A graphics driver uses either its implementation of the draw_rgb(Fl_RGB_Image *,....) - or that of the draw_fixed(Fl_RGB_Image *,....) member functions to draw an RGB image. - Same thing with draw_bitmap(Fl_Bitmap *,....) or draw_fixed(Fl_Bitmap *,....). - Same thing with draw_pixmap(Fl_Pixmap *,....) or draw_fixed(Fl_Pixmap *,....). - - The driver uses draw_???() if it can directly map the image data, + A graphics driver can implement up to 6 virtual member functions to draw images: + virtual void draw_pixmap(Fl_Pixmap *pxm,int XP, int YP, int WP, int HP, int cx, int cy) + virtual void draw_bitmap(Fl_Bitmap *bm,int XP, int YP, int WP, int HP, int cx, int cy) + virtual void draw_rgb(Fl_RGB_Image *rgb,int XP, int YP, int WP, int HP, int cx, int cy) +and + virtual void draw_fixed(Fl_Pixmap *pxm,int XP, int YP, int WP, int HP, int cx, int cy) + virtual void draw_fixed(Fl_Bitmap *bm,int XP, int YP, int WP, int HP, int cx, int cy) + virtual void draw_fixed(Fl_RGB_Image *rgb,int XP, int YP, int WP, int HP, int cx, int cy) + - The 1st group of functions is used when the driver can directly map the image data, sized at data_w() x data_h(), to the image drawing area, sized at w()*scale x h()*scale where scale is the current GUI scale factor. - - If the driver does not support such scale-and-draw operation, it should use draw_fixed() - which is called by the library after the image has been internally resized to the adequate - drawing size and cached. - - The platform-independent Fl_Graphics_Driver class implements draw_???(image-class *,....) - that scales the image and calls the platform-specific implementation of - draw_fixed(image-class *,....) with the scaled, cached image. - - Some graphics drivers implement only draw_???() or draw_fixed() as in these examples: + - If the driver does not support such scale-and-draw operation, it should implement the + draw_fixed() function which is called by the library after the image has been internally + resized to the drawing size and cached. + - The platform-independent Fl_Graphics_Driver class implements the 1st group of functions. + Each resizes the image, caches it, and calls the platform-specific implementation of + draw_fixed(image-class *,....) with the cached image. + - Consider an image object, say from class Fl_RGB_Image. Fl_RGB_Image::draw() + calls the virtual member function draw_rgb(Fl_RGB_Image *,....). If Fl_XXX_Graphics_Driver + re-implements this function, this code runs and is expected to draw the image + adequately scaled to its drawing size. If Fl_XXX_Graphics_Driver does not re-implement + this function, Fl_Graphics_Driver::draw_rgb(Fl_RGB_Image *,....) runs. It internally + resizes the image, caches it, and calls Fl_XXX_Graphics_Driver::draw_fixed(Fl_RGB_Image *,....) + that draws the image from its cached form which already has the adequate size. + - Some drivers implement, for a given image class, only the function of the 1st group or + only draw_fixed() as in these examples: - Fl_Quartz_Graphics_Driver implements only draw_rgb(Fl_RGB_Image *,....) because it can perform the scale-and-draw operation whatever the RGB image and the required scaling. - Fl_GDI_Graphics_Driver implements only draw_fixed(Fl_Pixmap *,....). The library - takes care of scaling and caching the Pixmap to the adequate drawing size. - - Some drivers implement both draw_???() and draw_fixed() : + takes care of resizing and caching the Pixmap to the adequate drawing size. + - Some drivers implement one function from both groups for a given image class : - Fl_Xlib_Graphics_Driver implements both draw_rgb(Fl_RGB_Image *,....) and draw_fixed(Fl_RGB_Image *,....) because scale-and-draw is possible only in the presence of Xrender. In the absence of Xrender, the draw_rgb() implementation calls |