绘图时防止闪烁 [英] Prevent Flickering When Drawing

问题描述

所以我有以下代码在屏幕上绘制矩形:

So I have this code to draw a rectangle on my screen:

LOGBRUSH m_LogBrush;
HBRUSH m_hBrush;
HPEN m_hPen;

HDC m_hDC;

void DrawBox(int x, int y, int r, int g, int b, int size, int thickness)
{
    // Brush style to hollow
    m_LogBrush.lbStyle = BS_NULL;

    // Create a logical brush and select into the context
    m_hBrush = CreateBrushIndirect(&m_LogBrush);
    SelectObject(m_hDC, m_hBrush);

    // Create a logical pen and select into the context
    m_hPen = CreatePen(PS_SOLID, thickness, RGB(r, g, b));
    SelectObject(m_hDC, m_hPen);

    // Draw the rectangle
    Rectangle(m_hDC, (x - size / 2), (y - size / 2), (x + size / 2), (y + size / 2));

    // Remove the object
    DeleteObject(m_hBrush);
    DeleteObject(m_hPen);
}

但是，当在循环中反复被调用时，它会在屏幕上闪烁.我想知道是否有办法防止这种闪烁?

However, when being called repeatedly inside a loop it flickers on the screen. I was wondering if there was a way to prevent this flicker?

任何帮助将不胜感激.

谢谢

推荐答案

这不应是答案，但我不能在注释中张贴代码:

This should not be an answer, but I can not post code in comments:

您的代码中有很多GDI泄漏.

You have many GDI leaks in your code.

复制/粘贴以下代码，并在闪烁减少时向我们报告:

Copy/paste the following code and report us if flickering diminishes:

void DrawBox(int x, int y, int r, int g, int b, int size, int thickness)
{
    // Brush style to hollow
    m_LogBrush.lbStyle = BS_NULL;

    // Create a logical brush and select into the context
    m_hBrush = CreateBrushIndirect(&m_LogBrush);
    HBRUSH hbrOldBrush = SelectObject(m_hDC, m_hBrush);

    // Create a logical pen and select into the context
    m_hPen = CreatePen(PS_SOLID, thickness, RGB(r, g, b));
    HPEN hpOldPen = SelectObject(m_hDC, m_hPen);

    // Draw the rectangle
    Rectangle(m_hDC, (x - size / 2), (y - size / 2), (x + size / 2), (y + size / 2));

    // Remove the object
    SelectObject(m_hDC, hbrOldBrush);  // first you must restore DC to original state
    SelectObject(m_hDC, hpOldPen);     // same here
    DeleteObject(m_hBrush);
    DeleteObject(m_hPen);

}

在MSDN上阅读有关GDI泄漏的信息.

Read on MSDN about GDI leaks.

这应该减少闪烁，但是要完全消除闪烁，您应该执行以下操作:

This should diminish flickering, but to completely remove flickering you should do the following:

• 删除 CS_VREDRAW | CS_HREDRAW 从您的窗口类定义中；
响应

• Remove the CS_VREDRAW | CS_HREDRAW from your window class definition;
• return 1L in your window procedure ( or TRUE in your dialog box procedure ) in response to WM_ERASEBKGND;
• draw everything on a memory bitmap and then BitBlt it into your m_hDC -> this is called double buffering ( you can find many examples online );

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