From 9999b6526185ba007b85a3d892406296159385bb Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Thu, 3 Feb 2022 01:00:05 +0900
Subject: [PATCH] internal/uidriver/glfw: bug fix: a callback must be
 registered at createWindow

---
 internal/uidriver/glfw/ui.go | 40 +++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/internal/uidriver/glfw/ui.go b/internal/uidriver/glfw/ui.go
index 63ef1c722..7996007d0 100644
--- a/internal/uidriver/glfw/ui.go
+++ b/internal/uidriver/glfw/ui.go
@@ -711,6 +711,7 @@ func (u *UserInterface) createWindow() error {
 
 	u.registerWindowSetSizeCallback()
 	u.registerWindowCloseCallback()
+	u.registerWindowFramebufferSizeCallback()
 
 	return nil
 }
@@ -782,6 +783,28 @@ func (u *UserInterface) registerWindowCloseCallback() {
 	u.window.SetCloseCallback(u.closeCallback)
 }
 
+// registerWindowFramebufferSizeCallback must be called from the main thread.
+func (u *UserInterface) registerWindowFramebufferSizeCallback() {
+	if u.defaultFramebufferSizeCallback == 0 {
+		// When the window gets resized (either by manual window resize or a window
+		// manager), glfw sends a framebuffer size callback which we need to handle (#1960).
+		// This event is the only way to handle the size change at least on i3 window manager.
+		u.defaultFramebufferSizeCallback = glfw.ToFramebufferSizeCallback(func(_ *glfw.Window, w, h int) {
+			if u.isFullscreen() {
+				return
+			}
+
+			// The framebuffer size is always scaled by the device scale factor (#1975).
+			// See also the implementation in uiContext.updateOffscreen.
+			s := u.deviceScaleFactor(u.currentMonitor())
+			ww := int(float64(w) / s)
+			wh := int(float64(h) / s)
+			u.setWindowSizeInDIP(ww, wh, u.isFullscreen())
+		})
+	}
+	u.window.SetFramebufferSizeCallback(u.defaultFramebufferSizeCallback)
+}
+
 // waitForFramebufferSizeCallback waits for GLFW's FramebufferSize callback.
 // f is a process executed after registering the callback.
 // If the callback is not invoked for a while, waitForFramebufferSizeCallback times out and return.
@@ -905,23 +928,6 @@ func (u *UserInterface) init() error {
 		u.window.Maximize()
 	}
 
-	// When the window gets resized (either by manual window resize or a window
-	// manager), glfw sends a framebuffer size callback which we need to handle (#1960).
-	// This event is the only way to handle the size change at least on i3 window manager.
-	u.defaultFramebufferSizeCallback = glfw.ToFramebufferSizeCallback(func(_ *glfw.Window, w, h int) {
-		if u.isFullscreen() {
-			return
-		}
-
-		// The framebuffer size is always scaled by the device scale factor (#1975).
-		// See also the implementation in uiContext.updateOffscreen.
-		s := u.deviceScaleFactor(u.currentMonitor())
-		ww := int(float64(w) / s)
-		wh := int(float64(h) / s)
-		u.setWindowSizeInDIP(ww, wh, u.isFullscreen())
-	})
-	u.window.SetFramebufferSizeCallback(u.defaultFramebufferSizeCallback)
-
 	u.window.SetTitle(u.title)
 	u.window.Show()