[ghex/gtk4-port] Rewrite render_cursor

[Logan Rathbone <larathbone src gnome org>]

commit fb7b15e88c1e8407500cadb85885712fa700d7ab
Author: Logan Rathbone <poprocks gmail com>
Date:   Tue Sep 14 22:13:11 2021 -0400

    Rewrite render_cursor
    
    This should get the cursor rendering to work properly on both X11 and
    wayland now. The problem was, before gtkhex was basically guessing where
    to draw the cursor based on some janky assumptions, and then re-drawing
    the hex or ascii characters atop the drawing area.
    
    This is, of course, not the best approach, so the rewrite just uses the
    existing data from the pango layouts and draws the cursor using that
    data.

 src/gtkhex.c | 123 +++++++++++++++++++++++++++++------------------------------
 1 file changed, 60 insertions(+), 63 deletions(-)
---
diff --git a/src/gtkhex.c b/src/gtkhex.c
index 7f0e2b34..636171aa 100644
--- a/src/gtkhex.c
+++ b/src/gtkhex.c
@@ -557,28 +557,18 @@ invalidate_ac (GtkHex *gh)
 static void
 render_cursor (GtkHex *gh,
                cairo_t *cr,
+               GtkWidget *widget,
+               PangoLayout *layout,
+               int y,
                GtkHexViewType cursor_type)
 {
-       GdkRGBA bg_color;
        GdkRGBA fg_color;
+       int index;
+       int range[2];
        GtkStateFlags state;
        GtkStyleContext *context;
-       int cx, cy, i;
-       static char c[2];               /* zeroed by default, which we want. */
-       GtkWidget *widget;              /* shorthand for relevant drawing area */
-       PangoLayout *layout;    /* shorthand for relevant pango layout */
-       gboolean got_coords = FALSE;
-
-       if (cursor_type == VIEW_HEX)
-       {
-               widget = gh->xdisp;
-               layout = gh->xlayout;
-       }
-       else
-       {
-               widget = gh->adisp;
-               layout = gh->alayout;
-       }
+       cairo_region_t *region;
+       double x1, x2, y1, y2;
 
        g_return_if_fail (gtk_widget_get_realized (widget));
 
@@ -586,49 +576,59 @@ render_cursor (GtkHex *gh,
        state = gtk_widget_get_state_flags (widget);
 
        if (cursor_type == VIEW_HEX)
-               got_coords = get_xcoords (gh, gh->cursor_pos, &cx, &cy);
-       else
-               got_coords = get_acoords (gh, gh->cursor_pos, &cx, &cy);
-
-       /* Bail out in any event if we didn't get coordinates. */
-       if (! got_coords)
        {
-               g_critical("%s: Something has gone wrong. Can't get coordinates!",
-                               __func__);
-               return;
-       }
+               int spaces;
+
+               spaces = (gh->cursor_pos % gh->cpl) / gh->group_type;
+               index = 2 * (gh->cursor_pos % gh->cpl);
+               index += spaces;
 
-       /* Otherwise, continue. */
-       if (cursor_type == VIEW_HEX)
-       {
-               format_xbyte (gh, gh->cursor_pos, c);
                if (gh->lower_nibble) {
-                       cx += gh->char_width;
-                       i = 1;
+                       range[0] = index + 1;
+                       range[1] = index + 2;
                } else {
-                       c[1] = 0;
-                       i = 0;
+                       range[0] = index;
+                       range[1] = index + 1;
                }
        }
        else
        {
-               c[0] = gtk_hex_get_byte(gh, gh->cursor_pos);
-               if (! is_displayable (c[0]))
-                       c[0] = '.';
+               index = gh->cursor_pos % gh->cpl;
+               range[0] = index;
+               range[1] = index + 1;
        }
 
-       gtk_style_context_save (context);
+       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);
+
+       /* Render background - fill bg with default selection colour if we have
+        * focus on the pane in question; otherwise, draw a solid black box.
+        */
 
        if (gh->active_view == cursor_type)
        {
+               gtk_style_context_save (context);
+
                state |= GTK_STATE_FLAG_SELECTED;
                gtk_style_context_set_state (context, state);
 
                gtk_render_background (context, cr,
-                               cx,                                     /* double x, */
-                               cy,                                     /* double y, */
-                               gh->char_width,         /* double width, */
-                               gh->char_height - 1);   /* double height */
+                               x1,
+                               y1,
+                               ABS(x2-x1), 
+                               ABS(y2-y1));
+
+               gtk_render_layout (context, cr, 0, y, layout);
+
+               gtk_style_context_restore (context);
        }
        else
        {
@@ -637,24 +637,17 @@ render_cursor (GtkHex *gh,
                cairo_set_source_rgba (cr,
                                fg_color.red, fg_color.green, fg_color.blue,
                                fg_color.alpha);
-               cairo_set_line_width (cr, 1.0);
-               cairo_rectangle (cr, cx + 0.5, cy + 0.5, gh->char_width,
-                               gh->char_height - 1);
+               cairo_set_line_width (cr, 1.5);
+
+               cairo_rectangle (cr, x1, y1, ABS(x2-x1), ABS(y2-y1));
+
                cairo_stroke (cr);
                cairo_restore (cr);
        }
 
-       if (cursor_type == VIEW_HEX)
-       {
-               pango_layout_set_text (layout, &c[i], 1);
-       }
-       else
-       {
-               pango_layout_set_text (layout, c, 1);
-       }
+       /* Restore state from cairo_clip */
 
-       gtk_render_layout (context, cr, cx, cy, layout);
-       gtk_style_context_restore (context);
+       cairo_restore (cr);
 }
 
 static void
@@ -872,6 +865,8 @@ render_lines (GtkHex *gh,
        g_return_if_fail (gtk_widget_get_realized (GTK_WIDGET(gh)));
        g_return_if_fail (gh->cpl);
 
+       /* Setup variables depending on widget type (hex or ascii) */
+
        if (type == VIEW_HEX)
        {
                widget = gh->xdisp;
@@ -891,7 +886,6 @@ render_lines (GtkHex *gh,
        cursor_line = gh->cursor_pos / gh->cpl - gh->top_line;
        gtk_widget_get_allocation (widget, &allocation);
 
-       /* render background. */
        gtk_render_background (context, cr,
                        /* x: */                0,
                        /* y: */                min_lines * gh->char_height,
@@ -926,13 +920,16 @@ render_lines (GtkHex *gh,
                                /* x: */ 0,
                                /* y: */ i * gh->char_height,
                                layout);
-       }
 
-       if (cursor_line >= min_lines &&
-                       cursor_line <= max_lines &&
-                       gh->cursor_shown)
-       {
-               render_cursor (gh, cr, type);
+               if (i == cursor_line)
+               {
+                       render_cursor (gh,
+                                       cr,
+                                       widget,
+                                       layout,
+                                       i * gh->char_height,
+                                       type);
+               }
        }
 }