\nOnce you invent a new flag you can start using it to fix errors of the past\nwithout breaking backwards compatibility.\n<\/p>\n
\nOne of the errors of the past was that property sheet page dimensions\nwere taken relative to the “MS Sans Serif” font, even if the page\nused some other font.\n<\/p>\n
\nDLG_SAMPLE DIALOGEX 32, 32, 212, 188\nCAPTION \"Caption\"\nFONT \"Lucida Sans Unicode\"\n...\n<\/pre>\n\nThis sample dialog template says that it is 212dlu wide and 188dlu tall.\nIf the dialog template were used for a standalone dialog, those\nDLU values would be calculated relative to the font on the dialog,\nnamely Lucida Sans Unicode.\n<\/p>\n
\nHowever, if the dialog template were used for a property sheet page,\nearlier versions of Windows would interpret the values\n212 and 188 relative to the font of the\nproperty sheet frame<\/strong> (usually MS Sans Serif),\nnot relative to the font associated with the page itself.\nMany people worked around this problem by giving their pages\npre-adjusted sizes, so that when Windows measured the dialog against\nMS Sans Serif, the adjustments cancelled out.\n<\/p>\n
\nIn other words, suppose that Lucida Sans Unicode is 25% wider\nthan MS Sans Serif. (I’m just making up numbers.)\nThen to get a 212dlu-wide dialog relative to Lucida Sans Unicode,\nthe dialog template would specify a width of\n212dlu + 25% = 265dlu.\n<\/p>\n
\nSince people were now relying on this behavior, it couldn’t be\nchanged. If you went in and “fixed” it, all those pre-adjusted\ndialogs would come out at the wrong size.\n<\/p>\n