Re: trying to do a blinking text cursor

Hey Johnny D

> SDL_gpu

I'll use SDL_gpu - it must be portable if as it has Android.mk .  But I was
under the impression that SDL did gpu operations... I'm new..

Please share your solution (or we can discuss it in SDL_gpu forum if it's
off topic for the list)

Thanks
Jack.






On 7 August 2016 at 01:43, Jonathan Dearborn <[email protected]> wrote:

> To invert existing colors on a render target, you have to read the pixels
> first so you can calculate the inverted colors.  This is a very slow
> operation and should not be done lightly.
>
> The best way to do it nowadays (i.e. without direct video memory access)
> is to use a shader and keep the color calculations on the GPU.  I can't
> help any further than that with plain SDL (is anyone using shaders with
> SDL_Renderer?), but I can do it all in a couple minutes with SDL_gpu.
>
> Jonny D
>
>
>
> On Sat, Aug 6, 2016 at 11:20 AM, Jack Andrews <[email protected]> wrote:
>
>> Hi,
>>
>> I'm using SDL2 as it looks like the most cross-platform UI library out
>> there.  I don't want a GUI toolkit.
>>
>> I'm writing a very simple text editor and so far, the most challenging
>> thing has been showing a blinking cursor at the text insertion point.
>>
>> I think I can work how an SDL timer works, but I can't work out how to
>> invert the colours of a SDL_Rect at the insertion point.  How would I
>> implement a function:
>>
>>   int ColourInvert(SDL_Window*w, SDL_Renderer*rend, SDL_Rect area);
>>
>> ?
>>
>> here's my pseudo-code for my editor (had to trim all the editor stuff
>> out):
>>
>> SDL_Renderer*re;SDL_Window*w;TTF_Font*font;
>> int drawline(char*s){
>>   SDL_Surface*su=SDL_RenderText_Shaded(font,s,a,b));
>>   SDL_Texture*tx=SDL_CreateTextureFromSurface,(re,su));
>>   SDL_RenderCopy(re,tx,0,&rect));
>>   SDL_DestroyTexture(tx);
>>   SDL_FreeSurface(su);
>> }
>> main(){
>>   SDL_Init(SDL_INIT_EVERYTHING);TTF_Init();
>>   w=SDL_CreateWindow(x,a,a,y,z,SDL_WINDOW_SHOWN);
>>   re=SDL_CreateRenderer(w,-1,SDL_RENDERER_ACCELERATED);
>>   SDL_SetRenderDrawColor(g.v,255,255,255,255);
>>   SDL_RenderClear(g.v);
>>   SDL_RenderPresent(g.v);
>>   //message loop
>>   //a keypress changes a line
>>   // for each line in lines{drawline(line)}
>> }
>>
>> Thanks for all your work, guys,
>>
>>
>> Jack
>>
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>>
>>
>
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