Release v0.6.19: retry dropped copies and stabilize snippet integration

src/app.cpp

@@ -124,7 +124,13 @@ class Transaction
     {
         check();
         adopted.clear();
-        app.ownSequence = expected = writeClipboard(app.window, c);
+        // These are temporary transaction contents, not a user's clipboard entry.
+        // In particular, do not invite the Windows history service to read our
+        // sentinel while the target editor is trying to open the clipboard.
+        auto temporary = c;
+        const std::wstring exclusion = L"ExcludeClipboardContentFromMonitorProcessing";
+        temporary.formats.push_back({RegisterClipboardFormatW(exclusion.c_str()), exclusion, Bytes{0}});
+        app.ownSequence = expected = writeClipboard(app.window, temporary);
         // A concurrent writer can win immediately after CloseClipboard, before we read its sequence.
         // Never adopt that writer's sequence as our own and paste its content.
         if (GetClipboardOwner() != app.window)
@@ -146,6 +152,8 @@ class Transaction
             return {};
         }
         ULONGLONG deadline = GetTickCount64() + 2000;
+        ULONGLONG retryAt = GetTickCount64() + 250;
+        unsigned attempts = 1;
         DWORD changed = before;
         ULONGLONG stable = 0;
         bool changedAgain = false;
@@ -162,6 +170,21 @@ class Transaction
             }
             if (changed != before && GetTickCount64() - stable >= 60)
                 break;
+            // Native editors can silently drop Ctrl+C if another process has
+            // the clipboard open. Retry only while our sentinel is untouched;
+            // never overwrite a copy result or another application's content.
+            if (changed == before && attempts < 3 && GetTickCount64() >= retryAt &&
+                !GetOpenClipboardWindow())
+            {
+                check();
+                if (!valid() || GetClipboardSequenceNumber() != before)
+                    return {};
+                if (!chord(L'C', MOD_CONTROL))
+                    return {};
+                diagnosticEvent(L"Copy retry: clipboard unchanged after Ctrl+C");
+                ++attempts;
+                retryAt = GetTickCount64() + 250;
+            }
             Sleep(10);
         }
         if (changed == before || !valid())