当窗口离屏时，为什么 CreateDIBSection() 会失败？
我正在构建一个 Delphi 组件，以在 VCL 表单上嵌入 SDL 渲染表面。 只要创建 SDL 表面时表单显示在屏幕上，它就可以正常工作。 否则，它无法创建任何渲染纹理。
我跟踪 SDL 代码并最终得到以下函数调用，该函数调用失败（返回 NULL）：
data->hbm = CreateDIBSection(renderdata->memory_hdc, bmi, DIB_RGB_COLORS, &data->pixels, NULL, 0);
HDC 是由具有自己的 HWND 窗口句柄的控件所拥有的绘图上下文的有效句柄，该句柄已正确设置。 但是，当在屏幕外创建控件时（这在 Delphi 中很常见）（所有窗体及其控件都以隐藏状态创建，直到需要显示它们时），CreateDIBSection 调用将失败，直到控件实际可见。
另外，如果它是在屏幕上创建的，则隐藏并重新显示（例如，如果它在选项卡上并且我切换选项卡），我创建的任何纹理都会在此过程中被清空。
这让我抓狂。 有人知道发生了什么事以及我该如何解决它吗？
I'm building a Delphi component to embed an SDL rendering surface on a VCL form. It works just fine as long as the form is on-screen at the moment that the SDL surface is created. Otherwise, it's not able to create any rendering textures.
I traced into the SDL code and ended up with the following function call, which fails (returns NULL):
data->hbm = CreateDIBSection(renderdata->memory_hdc, bmi, DIB_RGB_COLORS, &data->pixels, NULL, 0);
The HDC is a valid handle to the drawing context owned by a control that has its own HWND window handle, that's been set up properly. But when the control is created offscreen, which commonly happens in Delphi, (all forms, with their controls, are created in a hidden state until it's time to display them,) the CreateDIBSection call will fail until the control is actually visible.
Also, if it's created onscreen, then hidden and re-shown (if it's on a tab sheet and I switch tabs, for example,) any textures I create get blanked during this process.
This is driving me nuts. Anyone know what's going on and how I can work around it?
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绘图上下文仅在 Paint 处理期间有效。
The drawing context is only valid during Paint processing.