[ghex/gtk4-port] gtkhex: Rewrite render_cursor

[Logan Rathbone <larathbone src gnome org>]

commit d764d674a0e964066b93362b5ac3085df642217d
Author: Logan Rathbone <poprocks gmail com>
Date:   Thu Sep 30 11:36:17 2021 -0400

    gtkhex: Rewrite render_cursor
    
    This should de-jankify highlighting on wayland and keep it at parity
    with X11.
    
    There were similar issues to the cursor rendering. Assumptions were made
    based on multiplications of calculated character widths to decide the
    x/y coordinates and widths of the highlights.
    
    This, again, was a broken approach. We now just pull that information
    from pango and gdk, and render as necessary.

 src/gtkhex.c | 93 ++++++++++++++++++++++++++++++++----------------------------
 1 file changed, 49 insertions(+), 44 deletions(-)
---
diff --git a/src/gtkhex.c b/src/gtkhex.c
index 636171aa..ce9c275c 100644
--- a/src/gtkhex.c
+++ b/src/gtkhex.c
@@ -420,20 +420,6 @@ get_char_width (GtkHex *gh)
        return width;
 }
 
-static void
-format_xbyte (GtkHex *gh, int pos, char buf[2])
-{
-       guint low, high;
-       guchar c;
-
-       c = gtk_hex_get_byte(gh, pos);
-       low = c & 0x0F;
-       high = (c & 0xF0) >> 4;
-       
-       buf[0] = ((high < 10)?(high + '0'):(high - 10 + 'A'));
-       buf[1] = ((low < 10)?(low + '0'):(low - 10 + 'A'));
-}
-
 /*
  * format_[x|a]block() formats contents of the buffer
  * into displayable text in hex or ascii, respectively
@@ -675,19 +661,28 @@ render_highlights (GtkHex *gh,
        GtkHex_AutoHighlight *nextList = gh->auto_highlight;
        GtkStateFlags state;
        GtkStyleContext *context;
-       GtkWidget *widget;      /* shorthand for the hex or ascii drawing area */
+       GtkWidget *widget;              /* shorthand for the hex or ascii drawing area */
+       PangoLayout *layout;    /* shorthand for the hex or ascii pango layout */
        int hex_cpl;
+       cairo_region_t *region;
+       int y;
+       int range[2];
+       double x1, x2, y1, y2;
 
        if (type == VIEW_HEX)
        {
                widget = gh->xdisp;
+               layout = gh->xlayout;
        }
        else
        {
                widget = gh->adisp;
+               layout = gh->alayout;
        }
 
        hex_cpl = gtk_hex_layout_get_hex_cpl (GTK_HEX_LAYOUT(gh->layout_manager));
+       y = cursor_line * gh->char_height;
+
        context = gtk_widget_get_style_context (widget);
        gtk_style_context_save (context);
 
@@ -703,7 +698,7 @@ render_highlights (GtkHex *gh,
                                curHighlight->min_select)
                {
                        int start, end;
-                       int sl, el;
+                       int start_line, end_line;
                        int cursor_off = 0;
                        int len;
 
@@ -711,15 +706,16 @@ render_highlights (GtkHex *gh,
 
                        start = MIN(curHighlight->start, curHighlight->end);
                        end = MAX(curHighlight->start, curHighlight->end);
-                       sl = curHighlight->start_line;
-                       el = curHighlight->end_line;
+                       start_line = curHighlight->start_line;
+                       end_line = curHighlight->end_line;
 
-                       if (cursor_line == sl)
+                       if (cursor_line == start_line)
                        {
                                if (type == VIEW_HEX)
                                {
                                        cursor_off = 2 * (start % gh->cpl) + (start % gh->cpl) / 
gh->group_type;
-                                       if (cursor_line == el)
+
+                                       if (cursor_line == end_line)
                                                len = 2*(end%gh->cpl + 1) + (end%gh->cpl)/gh->group_type;
                                        else
                                                len = hex_cpl;
@@ -729,21 +725,17 @@ render_highlights (GtkHex *gh,
                                else
                                {
                                        cursor_off = start % gh->cpl;
-                                       if (cursor_line == el)
+
+                                       if (cursor_line == end_line)
                                                len = end - start + 1;
                                        else
                                                len = gh->cpl - cursor_off;
                                }
 
-                               if (len > 0) {
-                                       gtk_render_background (context, cr,
-                                                       cursor_off * gh->char_width,
-                                                       cursor_line * gh->char_height,
-                                                       len * gh->char_width,
-                                                       gh->char_height);
-                               }
+                               range[0] = cursor_off;
+                               range[1] = cursor_off + len;
                        }
-                       else if (cursor_line == el)
+                       else if (cursor_line == end_line)
                        {
                                if (type == VIEW_HEX)
                                {
@@ -754,24 +746,36 @@ render_highlights (GtkHex *gh,
                                {
                                        cursor_off = end % gh->cpl + 1;
                                }
-                               if (cursor_off > 0) {
-                                       gtk_render_background (context, cr,
-                                                        0,
-                                                        cursor_line * gh->char_height,
-                                                        cursor_off * gh->char_width,
-                                                        gh->char_height);
-                               }
+
+                               range[0] = 0;
+                               range[1] = cursor_off;
                        }
-                       else if (cursor_line > sl && cursor_line < el)
+                       else if (cursor_line > start_line && cursor_line < end_line)
                        {
                                int cpl = (type == VIEW_HEX) ? hex_cpl : gh->cpl;
 
-                               gtk_render_background (context, cr,
-                                                0,
-                                                cursor_line * gh->char_height,
-                                                cpl * gh->char_width,
-                                                gh->char_height);
+                               range[0] = 0;
+                               range[1] = cpl;
                        }
+
+                       region = gdk_pango_layout_get_clip_region (layout,
+                                       0,      /* x */
+                                       y,
+                                       range,
+                                       1);
+
+                       gdk_cairo_region (cr, region);
+                       cairo_save (cr);
+                       cairo_clip (cr);
+                       cairo_clip_extents (cr, &x1, &y1, &x2, &y2);
+
+                       gtk_render_background (context, cr,
+                                       x1,
+                                       y1,
+                                       ABS(x2-x1),
+                                       ABS(y2-y1));
+
+                       cairo_restore (cr);
                }
                curHighlight = curHighlight->next;
                while (curHighlight == NULL && nextList)
@@ -854,6 +858,7 @@ render_lines (GtkHex *gh,
                GtkHexViewType type)
 {
        GtkWidget *widget;
+       GtkStateFlags state;
        PangoLayout *layout;
        int (*format_func) (GtkHex *gh, char *out, int start, int end);
        GtkAllocation allocation;
@@ -910,12 +915,12 @@ render_lines (GtkHex *gh,
                if (tmp <= 0)
                        break;
 
-               render_highlights (gh, cr, i, type);
-
                pango_layout_set_text (layout,
                                (char *)gh->disp_buffer + (i - min_lines) * cpl,
                                MIN(cpl, tmp));
 
+               render_highlights (gh, cr, i, type);
+
                gtk_render_layout (context, cr,
                                /* x: */ 0,
                                /* y: */ i * gh->char_height,