[graf2d] allow zero-margins between pads and respect color for negative margins

[ferdymercury]

This Pull request:

Changes or fixes:

Fixes #20138

fyi @rlalik

Checklist:

• tested changes locally
• updated the docs (if necessary)

[github-actions]

Test Results

    22 files      22 suites   3d 17h 7m 53s ⏱️
 3 696 tests  3 671 ✅ 0 💤  25 ❌
79 361 runs  79 228 ✅ 0 💤 133 ❌

For more details on these failures, see this check.

Results for commit b6cbdf3.

♻️ This comment has been updated with latest results.

[rlalik]

I didn't test the PR code but this seems to be the solution. However, since this was broken and is being fixed, I would like to propose some change. Current behavior is that, when setting non-zero positive margin, the margin is applied to all pads, also on the outer edges, not only between pads. But sometimes one wants to increase the margin to separate the pads, for better visibility or so, but actually we don't want to increase the margin on the outer edges, where there is no other pad to keep distance from.

So my proposition would be, when the margin is positive, have all margins set - this will be the default behavior, compatible with 99% existing code. But when the margin value is negative, only the inner margin between pads are set, and the outer margin are kept 0. Setting margin to be 0 removes the margins between pads.

A such implementation would be flexible I think for almost all cases.

So with canvas->Divide(2, 2, -0.02, -0.02) I would get something like this:

and with canvas->Divide(2, 2, 0.02, -0.02) I would get something like this:

Could it be done?

[ferdymercury]

@rlalik would you like to propose a code modification for the new feature you are mentioning? It should go just below the if statement I modified

[rlalik]

@rlalik would you like to propose a code modification for the new feature you are mentioning? It should go just below the if statement I modified

So I propose that this gets merged and then I submit PR with my proposed change to add my requested feature.

[linev]

I reopen PR to restart CI