[[ Bug 22556 ]] Fix unpaired unlock of dragboard

montegoulding · montegoulding · commit 6f35144fd668 · 2020-02-07T11:59:20.000+11:00
This patch fixes an issue where `MCdragboard-&gt;Unlock()` was called when the
drag leaves the window when `MCdragboard-&gt;Lock()` had not been called. The
call to `Unlock()` has been changed to `PushUpdates()` so that the system
dragboard is updated with the current data so that it can be dropped onto
other applications etc. This change resolves an issue where after a number of
drags from LiveCode to another application drag and drop no longer appears to
function.
diff --git a/docs/notes/bugfix-22556.md b/docs/notes/bugfix-22556.md
@@ -0,0 +1 @@
+# Drag and drop on macOS from LiveCode to another application no longer fails after three drags
diff --git a/engine/src/clipboard.cpp b/engine/src/clipboard.cpp
@@ -76,6 +76,7 @@ bool MCClipboard::Lock(bool p_skip_pull) const
 
 bool MCClipboard::Unlock() const
 {
+    MCAssert(m_lock_count > 0);
     // Decrement the lock count. If it moves from one to zero, push any changes
     // out to the underlying OS clipboard.
     //
diff --git a/engine/src/dispatch.cpp b/engine/src/dispatch.cpp
@@ -1710,7 +1710,7 @@ void MCDispatch::wmdragleave(Window w)
 	}
     
     // We are no longer the drop target and no longer care about the drag data.
-    MCdragboard->Unlock();
+    MCdragboard->PushUpdates();
     MCdragboard->ReleaseData();
 	m_drag_target = false;
 }

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+# Drag and drop on macOS from LiveCode to another application no longer fails after three drags`
Original file line number	Diff line number	Diff line change
`@@ -76,6 +76,7 @@ bool MCClipboard::Lock(bool p_skip_pull) const`
`76`	`76`
`77`	`77`	`bool MCClipboard::Unlock() const`
`78`	`78`	`{`
	`79`	`+ MCAssert(m_lock_count > 0);`
`79`	`80`	`// Decrement the lock count. If it moves from one to zero, push any changes`
`80`	`81`	`// out to the underlying OS clipboard.`
`81`	`82`	`//`
Original file line number	Diff line number	Diff line change
`@@ -1710,7 +1710,7 @@ void MCDispatch::wmdragleave(Window w)`
`1710`	`1710`	`}`
`1711`	`1711`
`1712`	`1712`	`// We are no longer the drop target and no longer care about the drag data.`
`1713`		`- MCdragboard->Unlock();`
	`1713`	`+ MCdragboard->PushUpdates();`
`1714`	`1714`	`MCdragboard->ReleaseData();`
`1715`	`1715`	`m_drag_target = false;`
`1716`	`1716`	`}`