[Kst] extragear/graphics/kst/src/libkstmath

[Andrew Walker]

SVN commit 547619 by arwalker:

modify the value used to determine the scaling factor, and explain its significance

 M  +15 -1     kstpainter.cpp  


--- trunk/extragear/graphics/kst/src/libkstmath/kstpainter.cpp #547618:547619
@@ -62,7 +62,21 @@
   if (type() == P_PRINT || type() == P_EXPORT) {
     const QRect& w(window());
     
-    factor = (w.width() + w.height()) / 800;
+    //
+    // we want a line width of 1 to give a width of approximately 1 pt (where 1 pt = 1/72 
+    //  inch) when printing on letter sized paper. Assuming a margin of 0.25 inch in one 
+    //  direction (on both sides) and 0.5 inch in the other direction (again on both sides)
+    //  and a printer resolution of 600 dpi:
+    //
+    //  w.width() + w.height() = ( 8 + 11 - ( 2 * 0.5 ) - ( 2 * 0.25 ) ) * 600 = 10500
+    //
+    //  we want a scale factor of 600/72 = 8.333 in the line width, so our magic number simply 
+    //  becomes:
+    //
+    //  w.width() + w.height() / scale factor = 10200 / 8.333 ~ 1300
+    //
+    
+    factor = (w.width() + w.height()) / 1300;
   }
   
   return factor > 0 ? factor : 1;