除非指定较低的字体质量,否则ExtTextOut将失败,并且字符串非常长

Question

有时我们的应用程序需要使用ExtTextOut绘制非常长的字符串(例如6,000个字符).有时ExtTextOut失败并返回零,GetLastError也返回零.

要重新创建该情境,请创建一个简单的MFC Single Document应用程序,然后将OnDraw设置为:

void CTestExtTextView::OnDraw(CDC* pDC)
{
 CTestExtTextDoc* pDoc = GetDocument();
 ASSERT_VALID(pDoc);
 if (!pDoc)
  return;

 LOGFONT lfDetail = {0};
 lfDetail.lfHeight = -(::MulDiv(100, pDC->GetDeviceCaps(LOGPIXELSY), 720));
 lfDetail.lfCharSet = ANSI_CHARSET;
 lfDetail.lfOutPrecision = OUT_DEFAULT_PRECIS;
 lfDetail.lfQuality = CLEARTYPE_QUALITY;
 lfDetail.lfWeight = 400;
 _tcscpy_s(lfDetail.lfFaceName, LF_FACESIZE, _T("Arial"));

 CFont font;
 font.CreateFontIndirectW( &lfDetail );

 CFont * pold = pDC->SelectObject( &font );

 CString str = L"2 <office:document-content xmlns:office=\"urn:oasis:names:tc:opendocument:xmlns:office:1.0\" xmlns:style=\"urn:oasis:names:tc:opendocument:xmlns:style:1.0\" xmlns:text=\"urn:oasis:names:tc:opendocument:xmlns:text:1.0\" xmlns:table=\"urn:oasis:names:tc:opendocument:xmlns:table:1.0\" xmlns:draw=\"urn:oasis:names:tc:opendocument:xmlns:drawing:1.0\" xmlns:fo=\"urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" xmlns:dc=\"http://purl.org/dc/elements/1.1/\" xmlns:meta=\"urn:oasis:names:tc:opendocument:xmlns:meta:1.0\" xmlns:number=\"urn:oasis:names:tc:opendocument:xmlns:datastyle:1.0\" xmlns:presentation=\"urn:oasis:names:tc:opendocument:xmlns:presentation:1.0\" xmlns:svg=\"urn:oasis:names:tc:opendocument:xmlns:svg-compatible:1.0\" xmlns:chart=\"urn:oasis:names:tc:opendocument:xmlns:chart:1.0\" xmlns:dr3d=\"urn:oasis:names:tc:opendocument:xmlns:dr3d:1.0\" xmlns:math=\"http://www.w3.org/1998/Math/MathML\" xmlns:form=\"urn:oasis:names:tc:opendocument:xmlns:form:1.0\" xmlns:script=\"urn:oasis:names:tc:opendocument:xmlns:script:1.0\" xmlns:ooo=\"http://openoffice.org/2004/office\" xmlns:ooow=\"http://openoffice.org/2004/writer\" xmlns:oooc=\"http://openoffice.org/2004/calc\" xmlns:dom=\"http://www.w3.org/2001/xml-events\" xmlns:xforms=\"http://www.w3.org/2002/xforms\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" office:version=\"1.1\"><office:scripts/><office:font-face-decls><style:font-face style:name=\"Arial\" svg:font-family=\"Arial\" style:font-family-generic=\"swiss\" style:font-pitch=\"variable\"/><style:font-face style:name=\"Arial Unicode MS\" svg:font-family=\"&apos;Arial Unicode MS&apos;\" style:font-family-generic=\"system\" style:font-pitch=\"variable\"/><style:font-face style:name=\"Tahoma\" svg:font-family=\"Tahoma\" style:font-family-generic=\"system\" style:font-pitch=\"variable\"/></office:font-face-decls><office:automatic-styles><style:style style:name=\"co1\" style:family=\"table-column\"><style:table-column-properties fo:break-before=\"auto\" style:column-width=\"6.659cm\"/></style:style><style:style style:name=\"co2\" style:family=\"table-column\"><style:table-column-properties fo:break-before=\"auto\" style:column-width=\"7.408cm\"/></style:style><style:style style:name=\"co3\" style:family=\"table-column\"><style:table-column-properties fo:break-before=\"auto\" style:column-width=\"7.02cm\"/></style:style><style:style style:name=\"co4\" style:family=\"table-column\"><style:table-column-properties fo:break-before=\"auto\" style:column-width=\"7.214cm\"/></style:style><style:style style:name=\"co5\" style:family=\"table-column\"><style:table-column-properties fo:break-before=\"auto\" style:column-width=\"2.267cm\"/></style:style><style:style style:name=\"ro1\" style:family=\"table-row\"><style:table-row-properties style:row-height=\"0.473cm\" fo:break-before=\"auto\" style:use-optimal-row-height=\"true\"/></style:style><style:style style:name=\"ro2\" style:family=\"table-row\"><style:table-row-properties style:row-height=\"0.453cm\" fo:break-before=\"auto\" style:use-optimal-row-height=\"true\"/></style:style><style:style style:name=\"ta1\" style:family=\"table\" style:master-page-name=\"Default\"><style:table-properties table:display=\"true\" style:writing-mode=\"lr-tb\"/></style:style><style:style style:name=\"T1\" style:family=\"text\"><style:text-properties style:text-position=\"super 58%\"/></style:style></office:automatic-styles><office:body><office:spreadsheet><table:table table:name=\"Sheet1\" table:style-name=\"ta1\" table:print=\"false\"><office:forms form:automatic-focus=\"false\" form:apply-design-mode=\"false\"/><table:table-column table:style-name=\"co1\" table:default-cell-style-name=\"Default\"/><table:table-column table:style-name=\"co2\" table:default-cell-style-name=\"Default\"/><table:table-column table:style-name=\"co3\" table:default-cell-style-name=\"Default\"/><table:table-column table:style-name=\"co4\" table:default-cell-style-name=\"Default\"/><table:table-row table:style-name=\"ro1\"><table:table-cell office:value-type=\"string\"><text:p>Sample text for ExtTextOut</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>Second Column Sample Text</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>3<text:span text:style-name=\"T1\">rd</text:span> Column</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>A More Lengthly bit of text just to make sure we increase the size of the line to something that might make ExtTextOut fail. It doesn&apos;t actually fail if we switch to Anti-Aliased Fonts. Not sure why. It also doesn&apos;t fail if we make the text shorter.</text:p></table:table-cell></table:table-row><table:table-row table:style-name=\"ro1\"><table:table-cell office:value-type=\"string\"><text:p>Sample text for ExtTextOut</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>Second Column Sample Text</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>3<text:span text:style-name=\"T1\">rd</text:span> Column</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>A More Lengthly bit of text just to make sure we increase the size of the line to something that might make ExtTextOut fail. It doesn&apos;t actually fail if we switch to Anti-Aliased Fonts. Not sure why. It also doesn&apos;t fail if we make the text shorter.</text:p></table:table-cell></table:table-row><table:table-row table:style-name=\"ro1\"><table:table-cell office:value-type=\"string\"><text:p>Sample text for ExtTextOut</text:p></table:table-cell><table:table-cell office:value-type=\"string\"><text:p>Second Column Sample Text</text:p></table:table-cell><table:table-cell office:value-type=\"string\">";
 pDC->ExtTextOutW( 0,0, NULL, NULL, str, NULL );
 pDC->ExtTextOutW( 0,50, NULL, NULL, CString(L"But this will print out"), NULL );

 pDC->SelectObject( pold );
}

当你运行应用程序时,你会看到一行"但是这将在屏幕中间打印出来".如果你设置lfQuality = ANTIALIASED_QUALITY然后它确实打印出一些东西,但看起来不正确.

我在Vista和XP上测试了这个.

有任何想法吗？

Answer 1

我创建了一个简单的字体:

CFont font;
font.CreatePointFont(720, _T("Times New Roman"));
CFont * pold = pDC->SelectObject( &font );

然后初始化一个字符串,直到它无法打印.761个字符有效,762个字符失败:

CString str('a', 761); // Works
CString str('a', 762); // Fails

我尝试了不同的字体,它在更多的字符数下失败了.在我拿出每个字符串的大小之前没有意义:

CSize s = pDC->GetTextExtent(str);

两根弦的宽度均为~32700; 在16位符号限制32767附近.

我认为16位坐标限制从NT开始被提升到32位,所以我不知道为什么这在XP或Vista上不起作用.我可以依稀记得关于这个主题的知识库文章,但我找不到它.

我尝试使用TextOut和DrawText并得到了相同的结果.

然后我尝试绘制几行以确保它们超出了16位的限制:

pDC->MoveTo(10,0);
pDC->LineTo(10,38000);
pDC->MoveTo(10,38000);
pDC->LineTo(100, 38000);

它工作正常,所以我猜测基于文本的GDI函数存在一个错误.