internal/ui: bug fix: preserve cursor positions for toggling fullscreening for desktops

Updates #2475

internal/glfw/glfw_cglfw.go

@@ -178,6 +178,11 @@ func (w *Window) SetCharModsCallback(cbfun CharModsCallback) (previous CharModsC
 	return ToCharModsCallback(nil) // TODO
 }
 
+func (w *Window) SetCloseCallback(cbfun CloseCallback) (previous CloseCallback) {
+	w.w.SetCloseCallback(cbfun)
+	return ToCloseCallback(nil) // TODO
+}
+
 func (w *Window) SetCursor(cursor *Cursor) {
 	var c *cglfw.Cursor
 	if cursor != nil {
@@ -186,9 +191,8 @@ func (w *Window) SetCursor(cursor *Cursor) {
 	w.w.SetCursor(c)
 }
 
-func (w *Window) SetCloseCallback(cbfun CloseCallback) (previous CloseCallback) {
-	w.w.SetCloseCallback(cbfun)
-	return ToCloseCallback(nil) // TODO
+func (w *Window) SetCursorPos(xpos, ypos float64) {
+	w.w.SetCursorPos(xpos, ypos)
 }
 
 func (w *Window) SetDropCallback(cbfun DropCallback) (previous DropCallback) {

internal/glfw/glfw_goglfw.go

@@ -194,6 +194,19 @@ func (w *Window) SetCloseCallback(cbfun CloseCallback) (previous CloseCallback)
 	return f
 }
 
+func (w *Window) SetCursor(cursor *Cursor) {
+	if err := (*goglfw.Window)(w).SetCursor((*goglfw.Cursor)(cursor)); err != nil {
+		panic(err)
+	}
+}
+
+func (w *Window) SetCursorPos(xpos, ypos float64) {
+	if err := (*goglfw.Window)(w).SetCursorPos(xpos, ypos); err != nil {
+		panic(err)
+	}
+	return x, y
+}
+
 func (w *Window) SetDropCallback(cbfun DropCallback) (previous DropCallback) {
 	f, err := (*goglfw.Window)(w).SetDropCallback(cbfun)
 	if err != nil {
@@ -202,12 +215,6 @@ func (w *Window) SetDropCallback(cbfun DropCallback) (previous DropCallback) {
 	return f
 }
 
-func (w *Window) SetCursor(cursor *Cursor) {
-	if err := (*goglfw.Window)(w).SetCursor((*goglfw.Cursor)(cursor)); err != nil {
-		panic(err)
-	}
-}
-
 func (w *Window) SetFramebufferSizeCallback(cbfun FramebufferSizeCallback) (previous FramebufferSizeCallback) {
 	f, err := (*goglfw.Window)(w).SetFramebufferSizeCallback(cbfun)
 	if err != nil {

internal/ui/input_glfw.go

@@ -66,13 +66,27 @@ func (u *userInterfaceImpl) updateInputStateImpl() error {
 	for gb, ub := range glfwMouseButtonToMouseButton {
 		u.inputState.MouseButtonPressed[ub] = u.window.GetMouseButton(gb) == glfw.Press
 	}
-	cx, cy := u.window.GetCursorPos()
-	// TODO: This is tricky. Rename the function?
+
 	m := u.currentMonitor()
 	s := u.deviceScaleFactor(m)
-	cx = u.dipFromGLFWPixel(cx, m)
-	cy = u.dipFromGLFWPixel(cy, m)
-	cx, cy = u.context.clientPositionToLogicalPosition(cx, cy, s)
+
+	cx, cy := u.savedCursorX, u.savedCursorY
+	defer func() {
+		u.savedCursorX = math.NaN()
+		u.savedCursorY = math.NaN()
+	}()
+
+	if !math.IsNaN(cx) && !math.IsNaN(cy) {
+		cx2, cy2 := u.context.logicalPositionToClientPosition(cx, cy, s)
+		cx2 = u.dipToGLFWPixel(cx2, m)
+		cy2 = u.dipToGLFWPixel(cy2, m)
+		u.window.SetCursorPos(cx2, cy2)
+	} else {
+		cx2, cy2 := u.window.GetCursorPos()
+		cx2 = u.dipFromGLFWPixel(cx2, m)
+		cy2 = u.dipFromGLFWPixel(cy2, m)
+		cx, cy = u.context.clientPositionToLogicalPosition(cx2, cy2, s)
+	}
 
 	// AdjustPosition can return NaN at the initialization.
 	if !math.IsNaN(cx) && !math.IsNaN(cy) {
@@ -108,3 +122,11 @@ func (u *userInterfaceImpl) keyName(key Key) string {
 	})
 	return name
 }
+
+func (u *userInterfaceImpl) saveCursorPosition() {
+	u.m.Lock()
+	defer u.m.Unlock()
+
+	u.savedCursorX = u.inputState.CursorX
+	u.savedCursorY = u.inputState.CursorY
+}

internal/ui/ui_glfw.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"image"
+	"math"
 	"os"
 	"runtime"
 	"sync"
@@ -104,8 +105,10 @@ type userInterfaceImpl struct {
 
 	fpsModeInited bool
 
-	inputState InputState
-	iwindow    glfwWindow
+	inputState   InputState
+	iwindow      glfwWindow
+	savedCursorX float64
+	savedCursorY float64
 
 	sizeCallback                   glfw.SizeCallback
 	closeCallback                  glfw.CloseCallback
@@ -145,6 +148,8 @@ func init() {
 		fpsMode:                  FPSModeVsyncOn,
 		origWindowPosX:           invalidPos,
 		origWindowPosY:           invalidPos,
+		savedCursorX:             math.NaN(),
+		savedCursorY:             math.NaN(),
 	}
 	theUI.iwindow.ui = &theUI.userInterfaceImpl
 }
@@ -1403,6 +1408,10 @@ func (u *userInterfaceImpl) setFullscreen(fullscreen bool) {
 		return
 	}
 
+	if u.window.GetInputMode(glfw.CursorMode) == glfw.CursorDisabled {
+		u.saveCursorPosition()
+	}
+
 	// Enter the fullscreen.
 	if fullscreen {
 		u.disableWindowSizeLimits()