C Polymorphism, Partial redrawing (clipping?) and double-buffer update for my UI
Hello everyone,
Last time here I posted several questions in relation to creating a retained-mode UI. So far, the project has been going on smoothly, and I've taken a similar approach to what zraygui does (code from zraygui):
struct _widget {
Layout *parent;
Rectangle rect;
char *label;
WidgetType type;
Component *component;
bool visible;
bool active;
MouseEvent widgetStatus;
MouseListeners mouseListener;
};
The widgets share a common struct type Widget, but polymorphism happens inside the Component. It is an empty struct type, and for each type of widget, a pointer to their unique structs is cast as Component* into component. Then when manipulating the widget, the Component* is cast back to the original pointer type, enabling access to the fields.
I found this approach very smart, and I plan on implementing a similar thing (unless another better polymorphism exists in C). In my Widget struct, I have
typedef struct Widget {
Frame* parent;
Rect bounds;
bool active;
void *
void (*draw)(Widget *w);
}
Implementing partial rendering seemed easy, just redraw the exact area indicated by bounds, until i remembered I have to call EndDrawing() which swaps buffers. Hence, the updated widget will only exist on one buffer, and If I don't call EndDrawing(), inputs will not be polled.
I would like to create something similar to FLTK, which only renders the parts that need to be updated (AFAIK, I only studied a small part of the code yet, but it seems very interesting to learn about performant desktop UI systems)
So I have two ideas :
- Ditch the double buffer and write a custom "EndDrawing()" which does not swap but keeps all other functionality
- Draw to a render texture that I apply on both buffers. While exploring this idea, I realized that it could be beneficial for tooltips and floating windows, as they could be other textures overlaid on the main one.