C# TextRenderer.MeasureText 结果的准确性
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Accuracy of TextRenderer.MeasureText results
提问by Aidan Ryan
Calling TextRenderer.MeasureText as follows:
调用 TextRenderer.MeasureText 如下：
TextRenderer.MeasureText(myControl.Text, myControl.Font);
and comparing the result to the size of the control to check if text fits. The results are sometimes incorrect. Have observed the following two issues:
并将结果与控件的大小进行比较以检查文本是否适合。结果有时不正确。观察到以下两个问题：
- Often when a Label is set to AutoSize, TextRenderer will report a width that is 1 pixel wider than the auto-sized width of the Control.
- False negative where TextRenderer reports a width smaller than the control's but the text is still cut off. This occurred with "Estación de trabajo" -- not sure if the accent could somehow affect the width calculation?
- 通常，当 Label 设置为 AutoSize 时，TextRenderer 会报告比控件的自动调整大小的宽度宽 1 个像素的宽度。
- 假阴性，其中 TextRenderer 报告的宽度小于控件的宽度，但文本仍被切断。这发生在“Estación de trabajo”中——不确定重音是否会以某种方式影响宽度计算？
Is there any way to improve the accuracy of the MeasureText method? Should I be calling one of the overrides that accepts a device context and/or format flags?
有什么办法可以提高MeasureText方法的准确度吗？我应该调用接受设备上下文和/或格式标志的覆盖之一吗？
采纳答案by arbiter
Is there any way to improve the accuracy of the MeasureText method? Should I be calling one of the overrides that accepts a device context and/or format flags?
有什么办法可以提高MeasureText方法的准确度吗？我应该调用接受设备上下文和/或格式标志的覆盖之一吗？
You have answered your question by yourself. Actually MeasureText based on Win32 DrawTextEx, and this function cannot work without valid device context. So when you call MeasureText override without hdc, it internally create desktop compatible hdc to do measurement.
你已经自己回答了你的问题。实际上是基于 Win32 DrawTextEx 的 MeasureText，如果没有有效的设备上下文，此功能将无法工作。因此，当您在没有 hdc 的情况下调用 MeasureText 覆盖时，它会在内部创建与桌面兼容的 hdc 来进行测量。
Of course measurement depends on additional TextFormatFlags. Also keep in mind that Label painting (and measurement) depends on UseCompatibleTextRendering.
当然，测量取决于额外的 TextFormatFlags。还要记住，标签绘制（和测量）取决于UseCompatibleTextRendering。
So general conclusion you should use MeasureText for your own code, for example when you then call DrawText with exactly same parameters, in all other cases size returned by MeasureText cannot be treated as precise.
因此，一般结论您应该将 MeasureText 用于您自己的代码，例如，当您使用完全相同的参数调用 DrawText 时，在所有其他情况下，无法将 MeasureText 返回的大小视为精确。
If you need to get expected Label size, you should use GetPreferredSizemethod.
如果您需要获得预期的标签大小，您应该使用GetPreferredSize方法。
回答by Jason Hymanson
I don't know if I have a perfect solution but I ran into this when I was doing WinForms a few years back. The way I ended up compensating was by adjusting the returned measurement by a percentage. I cannot recall what I used (maybe 5% or 105?), but I do recall that I ended up using a constant percentage across the app and always rounded up.
我不知道我是否有完美的解决方案，但几年前我在做 WinForms 时遇到了这个问题。我最终补偿的方式是按百分比调整返回的测量值。我不记得我使用了什么（可能是 5% 或 105？），但我记得我最终在整个应用程序中使用了一个恒定的百分比并且总是四舍五入。
回答by fusi
Check out the TextFormatFlags parameter to this function:
查看此函数的 TextFormatFlags 参数：
TextRenderer::MeasureText(String, Font, Size, TextFormatFlags)
http://msdn.microsoft.com/en-us/library/8wafk2kt.aspx
http://msdn.microsoft.com/en-us/library/8wafk2kt.aspx
"The Size, in pixels, of text drawn on a single line with the specified font. You can manipulate how the text is drawn by using one of the DrawText overloads that takes a TextFormatFlags parameter. For example, the default behavior of the TextRenderer is to add padding to the bounding rectangle of the drawn text to accommodate overhanging glyphs. If you need to draw a line of text without these extra spaces you should use the versions of DrawText and MeasureText that take a Size and TextFormatFlags parameter. For an example, see MeasureText(IDeviceContext, String, Font, Size, TextFormatFlags)."
“在具有指定字体的单行上绘制的文本的大小（以像素为单位）。您可以使用采用 TextFormatFlags 参数的 DrawText 重载之一来操纵文本的绘制方式。例如，TextRenderer 的默认行为是将填充添加到绘制文本的边界矩形以容纳悬垂的字形。如果您需要绘制一行没有这些额外空格的文本，您应该使用采用 Size 和 TextFormatFlags 参数的 DrawText 和 MeasureText 版本。例如，请参阅 MeasureText(IDeviceContext, String, Font, Size, TextFormatFlags)。”
hth
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回答by anatolyArts
I know it's probably no actual anymore. Yet for future readers here is a simple yet accurate method of measuring text in a control:
我知道这可能不再是实际的了。然而，对于未来的读者，这里有一个简单而准确的方法来测量控件中的文本：
Graphics g=Graphics.FromHwnd(YOUR CONTROL HERE.Handle);
SizeF s=g.MeasureString("YOUR STRING HERE", Font, NULL, NULL, STRING LENGTH HERE, 1)
