window drag edge area is small

[dtorop]

Is there an existing issue for this?

• I checked and did not find my issue in the already reported ones

Describe the bug

When resizing the darktable main window, the drag area on the edge is quite thin, only one pixel. Compare this to Firefox on the same system, which has a drag handle area of approx. 11 pixels. The narrow drag region makes it difficult to easily resize the darktable window.

Steps to reproduce

1. Open darktable
2. Make sure the window is next full screen and does not cover the entire desktop.
3. Move mouse cursor to the edge of the window
4. Cursor will to a resize icon
5. Move mouse cursor just outside of the window
6. Cursor immediately changes to pointer icon or other appropriate angle for window/desktop area below the darktable window.

Expected behavior

There resize area should extend a few pixels beyond the edge of the window, to allow for easier resizing of the window.

Logfile | Screenshot | Screencast

Cursor in drag region of darktable window:

Cursor moved slightly and no longer in drag region of darktable window:

For comparison, cursor in drag region of Firefox window:

Cursor moved down and still in drag region of Firefox window:

Commit

This behavior started with 32764b0 which was to fix #19664.

Where did you obtain darktable from?

self compiled

darktable version

5.1.0+1989~gebb7ef77f3

What OS are you using?

Linux

What is the version of your OS?

Debian forky/sid

Describe your system

KDE Plasma 6.5.4 on Wayland, GTK 2.24.33, 32GB RAM

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

NVIDIA RTX 3080 laptop, 8GB, nvidia driver 550.163.01

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

Other desktop windows (e.g. Firefox, Emacs, or KDE System Settings) have a window shadow which corresponds somewhat to the region in which it is possible to use the mouse cursor resize the window. The darktable window does not have this shadow.

See #3307 and #3315 for potentially related work on this for Windows.

[dtorop]

Thinking this through a bit more. Though #19949 makes KDE look better, it's more of a patch than a proper solution. Here's a proposed fix:

• Add a hidden config option ui/decorations with option of auto (default), csd, or ssd
• When in csd mode or not running on Wayland, use the default titlebar/decorations. This matches behavior prior to 32764b0.
• When in ssd mode and running under Wayland, make a custom titlebar equivalent to the current top panel. It will include the clickable darktable logo and view selection. Use CSS to ensure there is a drag region to resize the window. The titlebar can be hidden/shown by the panels/top and panels/all actions, as with the current top panel.
• When ui/decorations is auto, use csd mode unless we can detect that we are running in Wayland/Gnome, in which case use ssd mode.

This is a conservative choice: fix behavior on Gnome, while not altering behavior on other desktop environments. If folks decided that the SSD mode is preferable, they can either manually switch to ssd or that can even become the new default for auto.

It may turn out that SSD is the way to go as it would provide more vertical screen space. And given that many (most?) darktable users work in fullscreen, this shouldn't even be a hard UI choice.