From b89d0837a679a05a3ac0e75a4dec8fd2de556d82 Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Sun, 5 Jun 2022 01:11:54 +1000
Subject: [PATCH] Qt: Avoid spamming resize events on paint

This caused long freezes on Windows when you dragged the window around,
because it was sending a paint event for every movement.
---
 pcsx2-qt/DisplayWidget.cpp | 28 ++++++++++++++++++----------
 pcsx2-qt/DisplayWidget.h   |  6 +++++-
 2 files changed, 23 insertions(+), 11 deletions(-)

diff --git a/pcsx2-qt/DisplayWidget.cpp b/pcsx2-qt/DisplayWidget.cpp
index e2e06731cb..90a93fe524 100644
--- a/pcsx2-qt/DisplayWidget.cpp
+++ b/pcsx2-qt/DisplayWidget.cpp
@@ -63,15 +63,15 @@ qreal DisplayWidget::devicePixelRatioFromScreen() const
 
 int DisplayWidget::scaledWindowWidth() const
 {
-	return static_cast<int>(std::ceil(static_cast<qreal>(width()) * devicePixelRatioFromScreen()));
+	return std::max(static_cast<int>(std::ceil(static_cast<qreal>(width()) * devicePixelRatioFromScreen())), 1);
 }
 
 int DisplayWidget::scaledWindowHeight() const
 {
-	return static_cast<int>(std::ceil(static_cast<qreal>(height()) * devicePixelRatioFromScreen()));
+	return std::max(static_cast<int>(std::ceil(static_cast<qreal>(height()) * devicePixelRatioFromScreen())), 1);
 }
 
-std::optional<WindowInfo> DisplayWidget::getWindowInfo() const
+std::optional<WindowInfo> DisplayWidget::getWindowInfo()
 {
 	WindowInfo wi;
 
@@ -104,9 +104,9 @@ std::optional<WindowInfo> DisplayWidget::getWindowInfo() const
 	}
 #endif
 
-	wi.surface_width = scaledWindowWidth();
-	wi.surface_height = scaledWindowHeight();
-	wi.surface_scale = devicePixelRatioFromScreen();
+	m_last_window_width = wi.surface_width = static_cast<u32>(scaledWindowWidth());
+	m_last_window_height = wi.surface_height = static_cast<u32>(scaledWindowHeight());
+	m_last_window_scale = wi.surface_scale = static_cast<float>(devicePixelRatioFromScreen());
 	return wi;
 }
 
@@ -236,11 +236,19 @@ bool DisplayWidget::event(QEvent* event)
 		{
 			QWidget::event(event);
 
-			const qreal dpr = devicePixelRatioFromScreen();
-			const int scaled_width = static_cast<int>(std::ceil(static_cast<qreal>(width()) * devicePixelRatioFromScreen()));
-			const int scaled_height = static_cast<int>(std::ceil(static_cast<qreal>(height()) * devicePixelRatioFromScreen()));
+			const float dpr = devicePixelRatioFromScreen();
+			const u32 scaled_width = static_cast<u32>(std::max(static_cast<int>(std::ceil(static_cast<qreal>(width()) * dpr)), 1));
+			const u32 scaled_height = static_cast<u32>(std::max(static_cast<int>(std::ceil(static_cast<qreal>(height()) * dpr)), 1));
+
+			// avoid spamming resize events for paint events (sent on move on windows)
+			if (m_last_window_width != scaled_width || m_last_window_height != scaled_height || m_last_window_scale != dpr)
+			{
+				m_last_window_width = scaled_width;
+				m_last_window_height = scaled_height;
+				m_last_window_scale = dpr;
+				emit windowResizedEvent(scaled_width, scaled_height, dpr);
+			}
 
-			emit windowResizedEvent(scaled_width, scaled_height, dpr);
 			return true;
 		}
 
diff --git a/pcsx2-qt/DisplayWidget.h b/pcsx2-qt/DisplayWidget.h
index 1df5577551..74106879c0 100644
--- a/pcsx2-qt/DisplayWidget.h
+++ b/pcsx2-qt/DisplayWidget.h
@@ -34,7 +34,7 @@ public:
 	int scaledWindowHeight() const;
 	qreal devicePixelRatioFromScreen() const;
 
-	std::optional<WindowInfo> getWindowInfo() const;
+	std::optional<WindowInfo> getWindowInfo();
 
 	void setRelativeMode(bool enabled);
 
@@ -55,6 +55,10 @@ private:
 	QPoint m_relative_mouse_last_position{};
 	bool m_relative_mouse_enabled = false;
 	std::vector<int> m_keys_pressed_with_modifiers;
+
+	u32 m_last_window_width = 0;
+	u32 m_last_window_height = 0;
+	float m_last_window_scale = 1.0f;
 };
 
 class DisplayContainer final : public QStackedWidget