perf: add signal to invalidate buffers without doing layout (#5123)

src/singletons/WindowManager.cpp

@@ -211,6 +211,11 @@ void WindowManager::forceLayoutChannelViews()
     this->layoutChannelViews(nullptr);
 }
 
+void WindowManager::invalidateChannelViewBuffers(Channel *channel)
+{
+    this->invalidateBuffersRequested.invoke(channel);
+}
+
 void WindowManager::repaintVisibleChatWidgets(Channel *channel)
 {
     this->layoutRequested.invoke(channel);
@@ -407,10 +412,10 @@ void WindowManager::initialize(Settings &settings, const Paths &paths)
         this->forceLayoutChannelViews();
     });
     settings.alternateMessages.connect([this](auto, auto) {
-        this->forceLayoutChannelViews();
+        this->invalidateChannelViewBuffers();
     });
     settings.separateMessages.connect([this](auto, auto) {
-        this->forceLayoutChannelViews();
+        this->invalidateChannelViewBuffers();
     });
     settings.collpseMessagesMinLines.connect([this](auto, auto) {
         this->forceLayoutChannelViews();

src/singletons/WindowManager.hpp

@@ -66,6 +66,10 @@ public:
     // This is called, for example, when the emote scale or timestamp format has
     // changed
     void forceLayoutChannelViews();
+
+    // Tell a channel (or all channels if channel is nullptr) to invalidate all paint buffers
+    void invalidateChannelViewBuffers(Channel *channel = nullptr);
+
     void repaintVisibleChatWidgets(Channel *channel = nullptr);
     void repaintGifEmotes();
 
@@ -124,6 +128,9 @@ public:
     // This signal fires whenever views rendering a channel, or all views if the
     // channel is a nullptr, need to redo their layout
     pajlada::Signals::Signal<Channel *> layoutRequested;
+    // This signal fires whenever views rendering a channel, or all views if the
+    // channel is a nullptr, need to invalidate their paint buffers
+    pajlada::Signals::Signal<Channel *> invalidateBuffersRequested;
 
     pajlada::Signals::NoArgSignal wordFlagsChanged;