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PixelPaint: Fix first undo action not working

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This commit is contained in:
Marco Cutecchia 2021-10-03 01:05:06 +02:00 • committed by Andreas Kling
parent c7431da3f2
commit 80e70f95ab
1 changed files with 24 additions and 12 deletions
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36
Userland/Applications/PixelPaint/ImageEditor.cpp
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@ -50,22 +50,34 @@ void ImageEditor::did_complete_action()
bool ImageEditor::undo() bool ImageEditor::undo()
{ {
if (m_undo_stack->can_undo()) { if (!m_undo_stack->can_undo())
m_undo_stack->undo(); return false;
layers_did_change();
return true; /* Without this you need to undo twice to actually start undoing stuff.
} * This is due to the fact that the top of the UndoStack contains the snapshot of the currently
return false; * shown image but what we actually want to restore is the snapshot right below it.
* Doing "undo->undo->redo" restores the 2nd topmost snapshot on the stack while lowering the
* stack pointer only by 1. This is important because we want the UndoStack's pointer to always point
* at the currently shown snapshot, otherwise doing 'undo->undo->draw something else' would delete
* one of the snapshots.
* This works because UndoStack::undo first decrements the stack pointer and then restores the snapshot,
* while UndoStack::redo first restores the snapshot and then increments the stack pointer.
*/
m_undo_stack->undo();
m_undo_stack->undo();
m_undo_stack->redo();
layers_did_change();
return true;
} }
bool ImageEditor::redo() bool ImageEditor::redo()
{ {
if (m_undo_stack->can_redo()) { if (!m_undo_stack->can_redo())
m_undo_stack->redo(); return false;
layers_did_change();
return true; m_undo_stack->redo();
} layers_did_change();
return false; return true;
} }
void ImageEditor::paint_event(GUI::PaintEvent& event) void ImageEditor::paint_event(GUI::PaintEvent& event)