16dbdc64 changed the padding around the app icon in the titlebar to be
applied both vertically and horizontally rather than only horizontally
because it was more natural from a developer's perspective, but some users
complained about the smaller icons in certain configurations.
So let's undo the change in 16dbdc64 and apply the icon padding only
horizontally for now.
We can add configurations for the icon padding (or icon size independent
from window.button.{width,height}?) later.
- fix that icons for normal/hovered/rounded buttons are not placed
exactly the same position
- fix blurry window button icons in scaled outputs
This commit introduces lab_img and scaled_img_buffer and uses them for
rendering icons in the window titlebar. Now the process of rendering
button icons are split into 2 phases: loading with lab_img_load() and
creating scene-nodes for them with scaled_img_buffer_create(). This
might incur some additional overhead since we no longer preload icon
textures, but the rendering of icon only happens for the first window
as backing buffers are shared and the overhead won't be noticeable.
This commit also simplifies the process of centering icon buffer in the
button, by creating icon buffers in a fixed geometry via
lab_img_render().
