如何用C#按固定像素滚动带自定义滚动条的窗口

问题根源 #

• 标准GetScrollInfo/SetScrollInfo仅对传统Win32原生滚动条生效，Chrome、Firefox、Visual Studio等现代应用普遍使用自定义滚动实现，完全不响应这类系统API。
• 鼠标滚轮消息的滚动步长由目标应用自行解析（比如Chrome的滚轮delta与实际滚动像素的比例受系统设置、页面缩放影响），无法保证跨应用的固定像素一致性。

解决方案：基于UI Automation的精确滚动 #

Windows UI Automation框架是系统级的自动化接口，可跨应用访问控件的滚动属性，无论目标窗口使用原生还是自定义滚动条，都能实现固定像素的精确滚动。

实现步骤 #

1. 获取目标窗口句柄（可通过前台窗口、标题匹配等方式）。
2. 通过UI Automation定位窗口内的可滚动主内容元素。
3. 调用ScrollPattern接口直接设置滚动位置，实现固定像素偏移。

完整代码示例 #

需先引用UIAutomationClient和UIAutomationTypes程序集（可通过NuGet安装或添加系统引用），并补充你原有代码中缺失的结构体/枚举定义：

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Windows.Automation;

public class WindowScroller
{
    // 获取前台窗口句柄
    [DllImport("user32.dll")]
    private static extern IntPtr GetForegroundWindow();

    // 从窗口句柄获取Automation根元素
    private static AutomationElement GetRootElement(IntPtr hwnd)
    {
        return AutomationElement.FromHandle(hwnd);
    }

    // 查找窗口内的可滚动元素
    private static AutomationElement FindScrollableElement(AutomationElement root)
    {
        var scrollCondition = new PropertyCondition(AutomationElement.IsScrollPatternAvailableProperty, true);
        return root.FindFirst(TreeScope.Descendants, scrollCondition);
    }

    // 垂直滚动固定像素
    public static bool ScrollVerticalByPixels(int pixelCount)
    {
        IntPtr hwnd = GetForegroundWindow();
        if (hwnd == IntPtr.Zero) return false;

        AutomationElement root = GetRootElement(hwnd);
        AutomationElement scrollableElement = FindScrollableElement(root);
        if (scrollableElement == null) return false;

        try
        {
            ScrollPattern scrollPattern = (ScrollPattern)scrollableElement.GetCurrentPattern(ScrollPattern.Pattern);
            if (!scrollPattern.Current.VerticallyScrollable) return false;

            // 计算滚动比例（像素转百分比）
            double totalScrollHeight = scrollPattern.Current.ScrollableHeight;
            double scrollPercentDelta = pixelCount / totalScrollHeight;
            double newVerticalPercent = scrollPattern.Current.VerticalScrollPercent + scrollPercentDelta;

            // 限制滚动范围在0-100%之间
            newVerticalPercent = Math.Clamp(newVerticalPercent, 0.0, 100.0);
            scrollPattern.SetScrollPercent(ScrollPattern.NoScroll, newVerticalPercent);
            return true;
        }
        catch (InvalidOperationException)
        {
            // 对不支持UI Automation的老旧应用，降级为键盘+小步滚轮模拟
            return SimulateFallbackScroll(pixelCount);
        }
    }

    // 降级滚动方案：模拟键盘箭头+小步滚轮
    private static bool SimulateFallbackScroll(int pixelCount)
    {
        // 系统默认箭头键滚动约15像素/次（可根据鼠标设置调整）
        int steps = Math.Abs(pixelCount) / 15;
        VirtualKeyCode key = pixelCount > 0 ? VirtualKeyCode.DOWN : VirtualKeyCode.UP;

        for (int i = 0; i < steps; i++)
        {
            InputHelpers.SendKeyPress(key);
        }

        // 处理剩余像素，用小delta滚轮补充
        int remainingPixels = Math.Abs(pixelCount) % 15;
        if (remainingPixels > 0)
        {
            int delta = remainingPixels * (pixelCount > 0 ? -120 : 120); // 系统默认120delta对应一行滚动
            InputHelpers.SendVerticalMouseWheel(delta);
        }
        return true;
    }
}

// 保留你原有的InputHelpers实现
internal class InputHelpers
{
    internal static bool SendKeyPress(VirtualKeyCode keyCode)
    {
        var manager = new InputManager();
        manager.SendKeyPress(keyCode);
        return manager.SendInputs();
    }

    internal static bool SendVerticalMouseWheel(int delta)
    {
        InputManager inputManager = new InputManager();
        inputManager.AddVerticalMouseWheel(delta);
        return inputManager.SendInputs();
    }

    internal static bool SendHorizontalMouseWheel(int delta)
    {
        InputManager inputManager = new InputManager();
        inputManager.AddHorizontalMouseWheel(delta);
        return inputManager.SendInputs();
    }
}

public class InputManager
{
    public List<INPUT> InputList { get; private set; }

    public InputManager()
    {
        InputList = new List<INPUT>();
    }

    internal void SendKeyPress(VirtualKeyCode key)
    {
        INPUT input = new INPUT();
        input.Type = InputType.InputKeyboard;
        input.Data.Keyboard = new KEYBDINPUT();
        input.Data.Keyboard.wVk = key;
        input.Data.Keyboard.dwFlags = KeyboardEventFlags.KEYEVENTF_KEYUP;
        InputList.Add(input);

        input = new INPUT();
        input.Type = InputType.InputKeyboard;
        input.Data.Keyboard = new KEYBDINPUT();
        input.Data.Keyboard.wVk = key;
        InputList.Add(input);
    }

    internal void AddVerticalMouseWheel(int delta)
    {
        INPUT input = new INPUT();
        input.Type = InputType.InputMouse;
        input.Data.Mouse = new MOUSEINPUT();
        input.Data.Mouse.dwFlags = MouseEventFlags.MOUSEEVENTF_WHEEL;
        input.Data.Mouse.mouseData = (uint)delta;
        InputList.Add(input);
    }

    internal void AddHorizontalMouseWheel(int delta)
    {
        INPUT input = new INPUT();
        input.Type = InputType.InputMouse;
        input.Data.Mouse = new MOUSEINPUT();
        input.Data.Mouse.dwFlags = MouseEventFlags.MOUSEEVENTF_HWHEEL;
        input.Data.Mouse.mouseData = (uint)delta;
        InputList.Add(input);
    }

    public bool SendInputs()
    {
        INPUT[] inputList = InputList.ToArray();
        uint len = (uint)inputList.Length;
        uint successfulInputs = NativeMethods.SendInput(len, inputList, Marshal.SizeOf(typeof(INPUT)));
        return successfulInputs == len;
    }
}

// 补充缺失的P/Invoke定义、结构体和枚举
public static class NativeMethods
{
    [DllImport("user32.dll")]
    public static extern uint SendInput(uint nInputs, [MarshalAs(UnmanagedType.LPArray), In] INPUT[] pInputs, int cbSize);
}

public enum InputType : uint
{
    InputMouse = 0,
    InputKeyboard = 1,
    InputHardware = 2
}

[Flags]
public enum KeyboardEventFlags : uint
{
    KEYEVENTF_EXTENDEDKEY = 0x0001,
    KEYEVENTF_KEYUP = 0x0002,
    KEYEVENTF_UNICODE = 0x0004,
    KEYEVENTF_SCANCODE = 0x0008
}

[Flags]
public enum MouseEventFlags : uint
{
    MOUSEEVENTF_WHEEL = 0x0800,
    MOUSEEVENTF_HWHEEL = 0x1000
}

public enum VirtualKeyCode : ushort
{
    UP = 0x26,
    DOWN = 0x28
}

[StructLayout(LayoutKind.Sequential)]
public struct INPUT
{
    public InputType Type;
    public InputUnion Data;
}

[StructLayout(LayoutKind.Explicit)]
public struct InputUnion
{
    [FieldOffset(0)] public MOUSEINPUT Mouse;
    [FieldOffset(0)] public KEYBDINPUT Keyboard;
    [FieldOffset(0)] public HARDWAREINPUT Hardware;
}

[StructLayout(LayoutKind.Sequential)]
public struct MOUSEINPUT
{
    public int dx;
    public int dy;
    public uint mouseData;
    public MouseEventFlags dwFlags;
    public uint time;
    public IntPtr dwExtraInfo;
}

[StructLayout(LayoutKind.Sequential)]
public struct KEYBDINPUT
{
    public VirtualKeyCode wVk;
    public ushort wScan;
    public KeyboardEventFlags dwFlags;
    public uint time;
    public IntPtr dwExtraInfo;
}

[StructLayout(LayoutKind.Sequential)]
public struct HARDWAREINPUT
{
    public uint uMsg;
    public ushort wParamL;
    public ushort wParamH;
}

关键说明 #

1. UI Automation核心优势：直接与应用的控件模型交互，完全绕过自定义滚动条的限制，对Chrome、VS、Office等现代应用均能实现精确滚动。
2. 降级机制：针对不支持UI Automation的老旧应用，自动切换为键盘+小步滚轮模拟，尽可能接近固定像素滚动效果。
3. 参数调整：SimulateFallbackScroll中15像素/箭头键的数值，可根据控制面板“鼠标-滚轮”中的“滚动行数”设置修改。

使用示例 #

// 向下滚动100像素
WindowScroller.ScrollVerticalByPixels(100);

// 向上滚动100像素
WindowScroller.ScrollVerticalByPixels(-100);

内容的提问来源于stack exchange，提问作者Ankur Tripathi