don't modify topIndex in handleTextChanged if control has not the focus

[tobiasmelcher]

fix split screen issue eclipse-platform/eclipse.platform.ui#2142 by not setting StyledText#topIndex if the control has not the focus.

[tobiasmelcher]

@mickaelistria would you prefer that we delete the complete if-block "if (!isFixedLineHeight() && topIndex > firstLine) {" or is the approach of this pull request also fine?

[github-actions]

Test Results

   383 files  ±0     383 suites  ±0   5m 12s ⏱️ -14s
 4 284 tests ±0   4 271 ✅ ±0  13 💤 ±0  0 ❌ ±0 
12 147 runs  ±0  12 064 ✅ ±0  83 💤 ±0  0 ❌ ±0 

Results for commit f0fcbe5. ± Comparison against base commit 37b22fb.

♻️ This comment has been updated with latest results.

[vogella]

We should try to delete the code that we do not know why it is there (eclipse-platform/eclipse.platform.ui#2142) early in the next release cycle to find if this causes any yet unknown issues.

[mickaelistria]

This PR looks good.

We should try to delete the code that we do not know why it is there

Here I think the reason for this code are clear enough: it can happen while editing some lines of non fixed height that the current position of the topIndex doesn't allow to see the whole first edited line. So I think it's best to keep it as proposed.

[tobiasmelcher]

test error
org.eclipse.swt.tests.junit.Test_org_eclipse_swt_custom_StyledText.test_notFixedLineHeightDoesntChangeLinePixelIfUnnecessary
might be related to this change? I need to check.

[mickaelistria]

might be related to this change?

That's extremely probable. Note that this test is important, it may not be written properly so maybe tweaking it so it is doing the job better can help, but in any case, the behavior it does test (notFixedLineHeightDoesntChangeLinePixelIfUnnecessary is hopefully explicit enough) is important to be guaranteed by a test. If this test is failing then it means that whenever a line header annotation is printed, the content of the text widget moves accordingly and may even hide (whose position is supposed to be stable for comfortable usage)