D16033: Fix double render when scrolling with visible search bar

[Mariusz Glebocki]

mglb created this revision.
mglb added a reviewer: Konsole.
mglb added a project: Konsole.
mglb requested review of this revision.

REVISION SUMMARY
  When the search bar is visible and user scrolls terminal contents,
  (part of) one line is rendered twice. The effect is visible on
  semi-transparent pixels (i.e. antialiasing) with some font sizes.
  
  With this patch, the characters which should be painted are calculated
  once. It was done for every rect in a paint region separately before.
  When two rectangles included different parts of a line, it was drawn
  twice. Only part of the line had visual effect visible, as each
  rectangle was cleared before rendering.
  
  F6310966: double-render-bug.png <https://phabricator.kde.org/F6310966>

TEST PLAN
  - set font to DejaVu Sans Mono 7pt (tested with 96dpi). Other
  
  fonts/sizes can work too, just make sure the bottom edge of the search
  box is not exactly between lines
  
  - run `printf '%3d▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒\n' $(seq 500)`
  - open search box
  - scroll up/down using mouse wheel
  
  Actual result: One line is brighter (painted twice)
  Expected result: All boxes should look the same

REPOSITORY
  R319 Konsole

BRANCH
  arc/Fix-double-render-when-scrolling-with-visible-searchbar (branched from master)

REVISION DETAIL
  https://phabricator.kde.org/D16033

AFFECTED FILES
  src/TerminalDisplay.cpp
  src/TerminalDisplay.h

To: mglb, #konsole
Cc: konsole-devel, herrold, ngraham, maximilianocuria, hindenburg
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