[SDL] SDL_RenderCopy android

wboe w.boeke at upcmail.nl
Sat Mar 9 01:05:48 PST 2013

Sam Lantinga wrote:

> You also can't use it on other platforms reliably.  The general recommendation on all platforms is to draw the entire scene each frame.  Hardware textures make this generally cheap.

Please don't forget that SDL is not used only for games, where it is quite normal to redraw the entire scene at every frame. 'Normal' applications however, e.g. musical instruments, consist of many small widgets that are modified now and then and only partially. Following your recommendation the developer would be forced to recalculate and redraw the whole screen even if only one small widget needs to be modified. Maybe the application has better things to do, e.g. calculate complex waveforms or animations.

Pure Android, without JNI, works perfectly also with partial screen updates. It is notable that after screen initialisation, the first time that one widget is modified, the entire screen is redrawn. Later on, only the widgets that are modified are recalculated and redrawn. The widgets are not double buffered, their shape is recalculated when needed. It would be very favourable if SDL for Android could mimic this behaviour.

I have the feeling that the problems as reported by the OP are similar to my experiences with SDL for Android tablets that I described two or three times in this forum. Next week I will get a very recent tablet that probably will show this bad behaviour clearly. I am hoping that my hacking skills will be sufficient to find a general solution!


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