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Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio

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On 6/11/23 20:07, Ben Bacarisse wrote:
> Blue-Maned_Hawk <bluemanedhawk@gmail.com> writes:
> 
> <snip/>
> 
>>                      XResizeWindow(display, window, fmax(width,
>>                      e.xconfigure.width), fmax(width, e.xconfigure.height));
> 
> Surely you wanted fmax(height, e.xconfigure.height) here?
> 

Oops, yes.  That was an accident.

>> cairo_xlib_surface_set_size(cairo_get_target(root_instance), fmax(width,
>> e.xconfigure.width), fmax(height, e.xconfigure.height));
> 
> This case looks odd.  What's the intent?  Do you want stop the user
> making the window narrower than width or shorted than height?  

Yes, i do.  I didn't know of any other way to do this.

>                                                               If that's
> what you want you should probably limit e.xconfigure.{width,height}, set
> the X window size and then carry on as before because you still need to
> set the offset and scale and offset the source in this case as well.
> 

How would i do that?

>>                  } else {
>>
>> cairo_xlib_surface_set_size(cairo_get_target(root_instance),
>> e.xconfigure.width, e.xconfigure.height);
>>                      if (e.xconfigure.width >= aspect_ratio *
>>                      e.xconfigure.height) {
>>                          cairo_translate(root_instance, (e.xconfigure.width
>>                         - e.xconfigure.height * aspect_ratio) / 2, 0);
>>                          cairo_scale(root_instance, (e.xconfigure.height *
>>                         aspect_ratio) / width, e.xconfigure.height /
>>                         height);
> 
> I'm pretty sure you did not intend to divide two integers here.  Both
> e.xconfigure.height and height have integer type.
> 
> But there's is a bigger issue.  To maintain the aspect ration, the x and y
> scaling should be the same.  Once you have decided whether it's the
> window width or the height that will determine the scaling, you should
> calculate the scale factor and use that in both arguments.
> 

…oh!  You're right!  It seems like replacing the cairo_scale() calls 
with cairo_scale(root_instance, (double)e.xconfigure.height / 
(double)height, (double)e.xconfigure.height / (double)height); and the 
corresponding call for the width case has worked!  Thank you so much!

>>          cairo_push_group(root_instance);
>>          cairo_set_source_rgb(root_instance, 0, 0, 0);
>>          cairo_paint(root_instance);
>>          cairo_set_source_surface(root_instance, surface, 0, 0);
>>          cairo_paint(root_instance);
>>          cairo_pop_group_to_source(root_instance);
>>          cairo_paint(root_instance);
>>          cairo_surface_flush(cairo_get_target(root_instance));
> 
> Do you realise that this is in the outer for (;;) loop?  That's a lot of
> busy work!
> 

In the actual application, the screen will be getting updated pretty 
much every frame, and the loop will be limited to only run once per frame.

-- 
⚗︎ | /blu.mɛin.dʰak/ | shortens to "Hawk" | he/him/his/himself/Mr.
bluemanedhawk.github.io
Bitches stole my whole ass ␔🭖᷿᪳𝼗᷍⏧𒒫𐻾ࣛ↉�⃣ quoted-printable, can't 
have shit in Thunderbird 😩

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Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio Blue-Maned_Hawk <bluemanedhawk@gmail.com> - 2023-06-11 19:13 -0400
  Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-06-12 01:07 +0100
    Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio Blue-Maned_Hawk <bluemanedhawk@gmail.com> - 2023-06-11 20:54 -0400
      Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-06-12 12:24 +0100
        Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-06-12 14:48 +0100
          Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio Blue-Maned_Hawk <bluemanedhawk@gmail.com> - 2023-06-12 14:23 -0400

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