selection rects, better initial y

src/pixie/fonts.nim

@@ -157,16 +157,25 @@ proc typeset*(
     result += font.typeface.getAdvance(runes[i])
     result *= font.scale
 
+  var fontUnitInitialY = font.typeface.ascent + font.typeface.lineGap / 2
+  if lineHeight != font.defaultLineHeight:
+    fontUnitInitialY += (
+      (lineHeight / font.scale) -
+      (font.typeface.ascent - font.typeface.descent + font.typeface.lineGap)
+    ) / 2
+  let initialY = round(fontUnitInitialY * font.scale)
+
   var
     at: Vec2
     prevCanWrap: int
-  at.y = round((font.typeface.ascent + font.typeface.lineGap / 2) * font.scale)
-  at.y += (lineheight - font.defaultLineHeight) / 2
+  at.y = initialY
   for i, rune in result.runes:
     if rune == LF:
+      let advance = font.typeface.getAdvance(SP) * font.scale
       result.positions[i] = at
       at.x = 0
       at.y += lineHeight
+      result.selectionRects[i] = rect(at.x, at.y - initialY, advance, lineHeight)
       prevCanWrap = 0
     else:
       if rune.canWrap():
@@ -185,6 +194,7 @@ proc typeset*(
             at.x += advance(font, result.runes, j, kerning)
 
       result.positions[i] = at
+      result.selectionRects[i] = rect(at.x, at.y - initialY, advance, lineHeight)
       at.x += advance
 
 iterator paths*(arrangement: Arrangement): Path =

tests/test_fonts.nim

@@ -533,3 +533,23 @@ Seventh line""",
   )
 
   doDiff(image, "lines1")
+
+block:
+  var font = readFont("tests/fonts/Roboto-Regular_1.ttf")
+  font.size = 18
+  font.lineHeight = 30
+
+  let image = newImage(200, 150)
+  image.fill(rgba(255, 255, 255, 255))
+  image.fillText(
+    font,
+    """First line
+Second line
+Third line
+Fourth line
+Fifth line""",
+    rgba(0, 0, 0, 255),
+    bounds = image.wh
+  )
+
+  doDiff(image, "lines2")