[v3] DnD Dropzones coordinates are incorrect on non-100% display scaling

[yulesxoxo]

Description

Fairly minimal repo to reproduce the problem: https://github.com/yulesxoxo/wails-dnd-dropzone-repro with videos and all that.

File drops were not registering correctly when display scaling was set to values other than 100%.

Setting the entire HTML content as a dropzone would work at 100% but at 200% scaling, dropping files would only register in the top left quadrant.

I believe the problem to be that the platform provides file drop coordinates in physical/device pixels, but document.elementFromPoint() expects CSS pixels (logical coordinates). Without conversion, at 150% scaling (devicePixelRatio = 1.5), a drop at physical coordinates (1200, 900) would be interpreted as CSS (1200, 900), causing elementFromPoint to look far outside the actual drop location.

#4632 only tested on Windows

To Reproduce

1. Create a Window and add a Listener for events.Common.WindowDropZoneFilesDropped
2. Add data-wails-dropzone to the top level <div> or <main> - at this point dropping a File anywhere in the window should trigger the Listener.
3. Set Display Scaling to any value that is not 100%, e.g. 200%

4. You'll see that only the top left quadrant will trigger the Listener and the rest of the Window no longer does. Instead you will see this in DevTools

Wails Runtime: Drop on element (or no element) at 1572,968 which is not a designated dropzone. Ignoring. Element: null

Expected behaviour

Wails runtime should factor in Scaling.

Screenshots

No response

Attempted Fixes

No response

System Details

Wails (v3.0.0-alpha.33)  Wails Doctor 
                                                                                                                                                                                        
# System 

┌────────────────────────────────────────────────────────────────────────────────────────────┐
| Name              | Windows 10 Pro                                                         |
| Version           | 2009 (Build: 26100)                                                    |
| ID                | 24H2                                                                   |
| Branding          | Windows 11 Pro                                                         |
| Platform          | windows                                                                |
| Architecture      | amd64                                                                  |
| Go WebView2Loader | true                                                                   |
| WebView2 Version  | 140.0.3485.94                                                          |
| CPU               | 13th Gen Intel(R) Core(TM) i7-13700K                                   |
| GPU 1             | NVIDIA GeForce RTX 4090 (NVIDIA) - Driver: 32.0.15.8129                |
| GPU 2             | Intel(R) UHD Graphics 770 (Intel Corporation) - Driver: 32.0.101.6987  |
| Memory            | 64GB                                                                   |
└────────────────────────────────────────────────────────────────────────────────────────────┘

# Build Environment 

┌────────────────────────────────┐
| Wails CLI    | v3.0.0-alpha.33 |
| Go Version   | go1.24.0        |
| -buildmode   | exe             |
| -compiler    | gc              |
| CGO_CFLAGS   |                 |
| CGO_CPPFLAGS |                 |
| CGO_CXXFLAGS |                 |
| CGO_ENABLED  | 1               |
| CGO_LDFLAGS  |                 |
| GOAMD64      | v1              |
| GOARCH       | amd64           |
| GOOS         | windows         |
└────────────────────────────────┘

# Dependencies 

┌────────────────────────────────────────────┐
| MakeAppx.exe (Windows SDK) | Not Installed |
| MSIX Packaging Tool        | Not Installed |
| SignTool.exe (Windows SDK) | Not Installed |
| npm                        | 10.9.3        |
| NSIS                       | Not Installed |
|                                            |
└───────── * - Optional Dependency ──────────┘

# Checking for issues 

 SUCCESS  No issues found

# Diagnosis 

 SUCCESS  Your system is ready for Wails development!

Additional context

No response

[WXjzcccc]

我碰到同样的问题。
这是由于Wails并没有处理缩放等级不为100%的情况。
当缩放等级不为100%时，Wails中关于坐标的信息都会错乱，例如window.setPosition(x,y)

I have the same problem.
This is because Wails does not handle the case where the system zoom level is not 100%.
When the system zoom level is not 100%, the coordinate information in Wails will be confused, such as window. setPosition(x, y)

在后端go中可以这样处理

In the backend, you can handle it like this

func getActiveWindowPosition(width, height int) (x, y int) {
	user32 := syscall.NewLazyDLL("user32.dll")
    procGetCursorPos := user32.NewProc("GetCursorPos")
	procGetSystemMetrics := user32.NewProc("GetSystemMetrics")
	procGetDpiForSystem := user32.NewProc("GetDpiForSystem")
	var p POINT
	// 获取当前鼠标的坐标
	ret, _, _ := procGetCursorPos.Call(uintptr(unsafe.Pointer(&p)))
	if ret == 0 {
		return 0, 0
	}
	// 获取当前屏幕尺寸
	retX, _, _ := procGetSystemMetrics.Call(SM_CXSCREEN)
	retY, _, _ := procGetSystemMetrics.Call(SM_CYSCREEN)
	if retX == 0 || retY == 0 {
		return 0, 0
	}
	// 获取系统DPI缩放比例
	dpi, _, _ := procGetDpiForSystem.Call()
	// 100%缩放对应96 DPI
	scaleFactor := float64(dpi) / 96.0
	logger.Infof("系统DPI: %d, 缩放比例: %.2f", dpi, scaleFactor)

	sX, sY := int(float64(retX)/scaleFactor), int(float64(retY)/scaleFactor)
	cX, cY := int(p.X), int(p.Y)

	// 考虑DPI缩放，将物理像素坐标转换为逻辑像素坐标
	// 在Wails中，窗口位置使用的是逻辑像素，而鼠标坐标是物理像素
	logicalX := int(float64(cX) / scaleFactor)
	logicalY := int(float64(cY) / scaleFactor)

	// 计算窗口左上角坐标，使鼠标位于窗口中心
	windowX := logicalX - width/2
	windowY := logicalY - height/2

	// 处理水平边界情况，确保窗口不超出屏幕
	if windowX < 0 {
		windowX = 0
	} else if windowX+width > sX {
		windowX = sX - width
	}

	// 处理垂直边界情况，确保窗口不超出屏幕
	if windowY < 0 {
		windowY = 0
	} else if windowY+height > sY {
		windowY = sY - height
	}

	logger.Infof("获取窗口坐标：X:%d,Y:%d", windowX, windowY)
	return windowX, windowY
}

因此这不仅仅是Dropzones的问题，可能需要对所有涉及到坐标的代码进行修改。

So this is not just a Dropzones issue, it may require modifications to all code that involves coordinates.

[exoticknight]

Although it's not really related to the issue, I want to ask where I can find the v3 DnD documents?