Clean up the baseline adjustment PR

docs/changelog.rst

@@ -7,6 +7,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 0.21.2 [future]
 ----------------------
 
+- A new :opt:`adjust_baseline` option to adjust the vertical alignment of text
+  inside a line (:pull:`3734`)
+
 - Fix a regression in 0.21.0 that broke rendering of private use unicode symbols followed
   by spaces, when they also exist not followed by spaces (:iss:`3729`)
 

kitty/core_text.m

@@ -323,6 +323,13 @@ harfbuzz_font_for_face(PyObject* s) {
     return self->hb_font;
 }
 
+static unsigned int
+adjust_ypos(unsigned int pos, unsigned int cell_height, int adjustment) {
+    if (adjustment >= 0) adjustment = MIN(adjustment, (int)pos - 1);
+    else adjustment = MAX(adjustment, (int)pos - (int)cell_height + 1);
+    return pos - adjustment;
+}
+
 void
 cell_metrics(PyObject *s, unsigned int* cell_width, unsigned int* cell_height, unsigned int* baseline, unsigned int* underline_position, unsigned int* underline_thickness, unsigned int* strikethrough_position, unsigned int* strikethrough_thickness) {
     // See https://developer.apple.com/library/content/documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/TypoFeatures/TextSystemFeatures.html
@@ -368,8 +375,9 @@ cell_metrics(PyObject *s, unsigned int* cell_width, unsigned int* cell_height, u
     CTLineGetTypographicBounds(line, &typographic_ascent, &typographic_descent, &typographic_leading);
     *cell_height = MAX(4u, (unsigned int)ceilf(line_height));
     CGFloat bounds_ascent = bounds_without_leading.size.height + bounds_without_leading.origin.y;
-    if (OPT(adjust_baseline_px) != 0) bounds_ascent -= OPT(adjust_baseline_px);
-    if (OPT(adjust_baseline_frac) != 0) bounds_ascent -= *cell_height * OPT(adjust_baseline_frac);
+    int baseline_offset = 0;
+    if (OPT(adjust_baseline_px) != 0) baseline_offset = OPT(adjust_baseline_px);
+    else if (OPT(adjust_baseline_frac) != 0) baseline_offset = *cell_height * OPT(adjust_baseline_frac);
     *baseline = (unsigned int)floor(bounds_ascent + 0.5);
     // Not sure if we should add this to bounds ascent and then round it or add
     // it to already rounded baseline and round again.
@@ -384,6 +392,11 @@ cell_metrics(PyObject *s, unsigned int* cell_width, unsigned int* cell_height, u
     debug("\tline metrics: ascent: %f descent: %f leading: %f\n", typographic_ascent, typographic_descent, typographic_leading);
     debug("\tfont metrics: ascent: %f descent: %f leading: %f underline_position: %f\n", self->ascent, self->descent, self->leading, self->underline_position);
     debug("\tcell_height: %u baseline: %u underline_position: %u strikethrough_position: %u\n", *cell_height, *baseline, *underline_position, *strikethrough_position);
+    if (baseline_offset) {
+        *baseline = adjust_ypos(*baseline, *cell_height, baseline_offset);
+        *underline_position = adjust_ypos(*underline_position, *cell_height, baseline_offset);
+        *strikethrough_position = adjust_ypos(*strikethrough_position, *cell_height, baseline_offset);
+    }
 
     CFRelease(test_frame); CFRelease(path); CFRelease(framesetter);
 

kitty/freetype.c

@@ -302,6 +302,14 @@ calc_cell_width(Face *self) {
     return ans;
 }
 
+
+static unsigned int
+adjust_ypos(unsigned int pos, unsigned int cell_height, int adjustment) {
+    if (adjustment >= 0) adjustment = MIN(adjustment, (int)pos - 1);
+    else adjustment = MAX(adjustment, (int)pos - (int)cell_height + 1);
+    return pos - adjustment;
+}
+
 void
 cell_metrics(PyObject *s, unsigned int* cell_width, unsigned int* cell_height, unsigned int* baseline, unsigned int* underline_position, unsigned int* underline_thickness, unsigned int* strikethrough_position, unsigned int* strikethrough_thickness) {
     Face *self = (Face*)s;
@@ -309,13 +317,13 @@ cell_metrics(PyObject *s, unsigned int* cell_width, unsigned int* cell_height, u
     *cell_height = calc_cell_height(self, true);
     int baseline_offset = 0;
     if (OPT(adjust_baseline_px) != 0) baseline_offset = OPT(adjust_baseline_px);
-    if (OPT(adjust_baseline_frac) != 0) baseline_offset = (int)(*cell_height * OPT(adjust_baseline_frac));
-    *baseline = font_units_to_pixels_y(self, self->ascender) - baseline_offset;
-    *underline_position = MIN(*cell_height - 1, (unsigned int)MAX(0, font_units_to_pixels_y(self, MAX(0, self->ascender - self->underline_position)) - baseline_offset));
+    else if (OPT(adjust_baseline_frac) != 0) baseline_offset = (int)(*cell_height * OPT(adjust_baseline_frac));
+    *baseline = font_units_to_pixels_y(self, self->ascender);
+    *underline_position = MIN(*cell_height - 1, (unsigned int)MAX(0, font_units_to_pixels_y(self, MAX(0, self->ascender - self->underline_position))));
     *underline_thickness = MAX(1, font_units_to_pixels_y(self, self->underline_thickness));
 
     if (self->strikethrough_position != 0) {
-      *strikethrough_position = MIN(*cell_height - 1, (unsigned int)MAX(0, font_units_to_pixels_y(self, MAX(0, self->ascender - self->strikethrough_position)) - baseline_offset));
+      *strikethrough_position = MIN(*cell_height - 1, (unsigned int)MAX(0, font_units_to_pixels_y(self, MAX(0, self->ascender - self->strikethrough_position))));
     } else {
       *strikethrough_position = (unsigned int)floor(*baseline * 0.65);
     }
@@ -324,6 +332,11 @@ cell_metrics(PyObject *s, unsigned int* cell_width, unsigned int* cell_height, u
     } else {
       *strikethrough_thickness = *underline_thickness;
     }
+    if (baseline_offset) {
+        *baseline = adjust_ypos(*baseline, *cell_height, baseline_offset);
+        *underline_position = adjust_ypos(*underline_position, *cell_height, baseline_offset);
+        *strikethrough_position = adjust_ypos(*strikethrough_position, *cell_height, baseline_offset);
+    }
 }
 
 unsigned int

kitty/options/definition.py

@@ -98,11 +98,12 @@ opt('adjust_baseline', '0',
     option_type='adjust_baseline', ctype='!adjust_baseline',
     add_to_default=False,
     long_text='''
-Adjust the baseline position of each character. You can use either
-a number, which is interpreted as pixels or a percentage (number followed by %),
-which is interpreted as the percentage of the line height. A positive
-value moves all characters up, and a negative value moves them down.
-The underline and strikethrough positions are adjusted accordingly.
+Adjust the vertical alignment of text (the height in the cell at which text is
+positioned). You can use either numbers, which are interpreted as pixels or a
+percentages (number followed by %), which are interpreted as the percentage of
+the line height. A positive value moves the baseline up, and a negative value
+moves them down. The underline and strikethrough positions are adjusted
+accordingly.
 '''
     )