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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.graphics.misc
Subject: Re: Running into problems while trying to scale Cairo surface to take up maximum space at specific aspect ratio
Date: Mon, 12 Jun 2023 12:24:31 +0100
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Blue-Maned_Hawk <bluemanedhawk@gmail.com> writes:

> On 6/11/23 20:07, Ben Bacarisse wrote:
>> Blue-Maned_Hawk <bluemanedhawk@gmail.com> writes:
<cut>
>>> 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?

You could change e.xconfigure.width (and height) but rather than do that
I'd base all the code on two new sizes

  int new_width = e.xconfigure.width, new_height = e.xconfigure.height;
  if (new_width < width || new_height < height) {
     new_width = fmax(width, new_width);
     ditto height
     set Xwindow size to new_width/new_height
  }
  what goes here is what was your else clause but using new_width and
  new_height rather than the e.xconfigure versions

<cut>
-- 
Ben.