Fix #22767: Ensure that the buttons are spaced to the size of the toolbar window, which is always visible.

[dan-masek]

resolves #22767

This fixes some of the problems -- when toolbars are created in one go, and some go outside the window bounds (when main client are becomes nothing), they will get sized correctly.

However, with WINDOW_NORMAL, some wonkiness still remains and blank buttons tend to appear once in a while (this might be due to the spacers).

Ideally, the trackbars should automatically resize to fit the width of the main window, when said window is resized (either manually when in NORMAL mode, or by code). This might however break some existing code that relies on current behaviour to place multiple trackbars on single row. Any opinions?

[AleksandrPanov]

Checked, the problem is reproduced, PR fixes the problem. Issue affects to 3.4, need to make a fix in 3.4

before fix:

after fix:

[alalek]

This patch should go into 3.4 branch first.
We will merge changes from 3.4 into 4.x regularly (weekly/bi-weekly).

Please:

• change "base" branch of this PR: 4.x => 3.4 (use "Edit" button near PR title)
• rebase your commits from 4.x onto 3.4 branch. For example:
  git rebase -i --onto upstream/3.4 upstream/4.x
  (check list of your commits, save and quit (Esc + "wq" + Enter)
  where upstream is configured by following this GitHub guide and fetched (git fetch upstream).
• push rebased commits into source branch of your fork (with --force option)

Note: no needs to re-open PR, apply changes "inplace".

[dan-masek]

Sounds good. I'm on the road for couple more days, I'll have a look at it over the weekend.

[alalek]

Thank you 👍