How Can I Eliminate Flickering in User Controls During Navigation?

Addressing User Control Flicker During Navigation

Navigating between User Controls often leads to visual flicker due to factors like repeated repainting and the use of background images. Even with various style adjustments, this problem can persist.

Understanding the Flicker Issue

The flicker stems from the rendering process. Each User Control paints its background image, creating temporary gaps where child controls are located. These gaps are briefly visible before the child controls repaint, and the contrast with the background image exacerbates the effect.

Why Standard Solutions Fail

Common double-buffering methods like OptimizedDoubleBuffer and UserPaint prove ineffective in this specific situation.

The Effective Solution: WS_EX_COMPOSITED

The root cause lies in how Windows handles control hierarchy rendering. Activating WS_EX_COMPOSITED for the form enables double-buffering at the form level, encompassing all child controls. This resolves the flicker.

protected override CreateParams CreateParams {
    get {
        CreateParams cp = base.CreateParams;
        cp.ExStyle |= 0x02000000;  // Enable WS_EX_COMPOSITED
        return cp;
    }
}

Further Performance Enhancements

These additional optimizations can significantly improve painting performance:

• BackgroundImageLayout: Set to "Tile" for efficient image scaling.
• Image Resizing: Pre-resize background images to match control dimensions to avoid runtime scaling.
• Pixel Format: Use Format32bppPArgb for faster background image rendering.
• WS_CLIPCHILDREN: Disable WS_CLIPCHILDREN to allow child controls to paint over the background, hiding the temporary gaps.

protected override CreateParams CreateParams {
    get {
        var parms = base.CreateParams;
        parms.Style &= ~0x02000000;  // Disable WS_CLIPCHILDREN
        return parms;
    }
}

Minimize Child Controls for Speed

Reducing the number of child controls dramatically boosts painting speed. Consider drawing simpler elements (text or images) directly within the User Control's OnPaint() method instead of relying on numerous child controls.

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