measure text string - win32 fonts

src/dlangui/graphics/fonts.d

@@ -18,6 +18,7 @@ class Font : RefCountedObject {
     abstract public @property string face();
     abstract public @property FontFamily family();
     abstract public @property bool isNull();
+	abstract public int measureText(const dchar[] text, ref int[] widths, int maxWidth);
     public void clear() {}
     public ~this() { clear(); }
 }

src/dlangui/platforms/windows/winapp.d

@@ -58,6 +58,40 @@ class Win32Font : Font {
 			_drawbuf = null;
 		}
     }
+	public override int measureText(const dchar[] text, ref int[] widths, int maxWidth) {
+		if (_hfont is null || _drawbuf is null || text.length == 0)
+			return 0;
+		wstring utf16text = toUTF16(text);
+		const wchar * pstr = utf16text.ptr;
+		uint len = cast(uint)utf16text.length;
+		GCP_RESULTSW gcpres;
+		gcpres.lStructSize = gcpres.sizeof;
+		if (widths.length < len + 1)
+			widths.length = len + 1;
+		gcpres.lpDx = widths.ptr;
+		gcpres.nMaxFit = len;
+		gcpres.nGlyphs = len;
+		uint res = GetCharacterPlacementW( 
+											 _drawbuf.dc,
+											 pstr,
+											 len,
+											 maxWidth,
+											 &gcpres,
+											 GCP_MAXEXTENT); //|GCP_USEKERNING
+		if (!res) {
+			widths[0] = 0;
+			return 0;
+		}
+		uint measured = gcpres.nMaxFit;
+		int total = 0;
+		for (int i = 0; i < measured; i++) {
+			int w = widths[i];
+			total += w;
+			widths[i] = total;
+		}
+		return measured;
+	}
+
 	public bool create(FontDef * def, int size, int weight, bool italic) {
         if (!isNull())
             clear();

winmain.d

@@ -3,6 +3,7 @@ module winmain;
 import dlangui.platforms.common.platform;
 import dlangui.widgets.widget;
 import dlangui.core.logger;
+import dlangui.graphics.fonts;
 import std.stdio;
 
 extern (C) int UIAppMain() {
@@ -14,5 +15,13 @@ extern (C) int UIAppMain() {
     window.mainWidget = myWidget;
     window.show();
     window.windowCaption = "New Window Caption";
+	FontRef font = FontManager.instance.getFont(32, 400, false, FontFamily.SansSerif, "Arial");
+	assert(!font.isNull);
+	int[] widths;
+	dchar[] text = cast(dchar[])"Test string"d;
+	int charsMeasured = font.measureText(text, widths, 1000);
+	assert(charsMeasured > 0);
+	int w = widths[charsMeasured - 1];
+	Log.d("Measured string: ", charsMeasured, " chars, width=", w);
     return Platform.instance().enterMessageLoop();
 }