[ghex] gtkhex: Make cursor appear on empty documents

[Logan Rathbone <larathbone src gnome org>]

commit 5130b8317f63f82d8089afaad2be68cbdeb3c8ed
Author: Logan Rathbone <poprocks gmail com>
Date:   Wed Dec 8 05:32:00 2021 -0500

    gtkhex: Make cursor appear on empty documents
    
    eg, for a newly created widget from a File->New operation, for the
    find/replace dialogs, etc.

 src/gtkhex.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)
---
diff --git a/src/gtkhex.c b/src/gtkhex.c
index 8b481d2..1a90fb1 100644
--- a/src/gtkhex.c
+++ b/src/gtkhex.c
@@ -604,7 +604,7 @@ render_cursor (GtkHex *gh,
        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.
+        * focus on the pane in question; otherwise, draw a solid box.
         */
        if (gh->active_view == cursor_type)
        {
@@ -898,7 +898,7 @@ render_lines (GtkHex *gh,
                format_func = format_xblock;
                cpl = gtk_hex_layout_get_hex_cpl (GTK_HEX_LAYOUT(gh->layout_manager));
        }
-       else
+       else    /* VIEW_ASCII */
        {
                widget = gh->adisp;
                layout = gh->alayout;
@@ -906,6 +906,8 @@ render_lines (GtkHex *gh,
                cpl = gh->cpl;
        }
 
+       /* Grab styling and render the (blank) background. */
+
        context = gtk_widget_get_style_context (widget);
        cursor_line = gh->cursor_pos / gh->cpl - gh->top_line;
        gtk_widget_get_allocation (widget, &allocation);
@@ -916,6 +918,20 @@ render_lines (GtkHex *gh,
                        /* width: */    allocation.width,
                        /* height: */   (max_lines - min_lines + 1) * gh->char_height);
 
+       /* If it's a blank canvass, we know there'll be no lines to render. But we
+        * draw a single space in the pango layout as a workaround for the fact
+        * that it will have no context as to how large to draw the cursor.
+        */
+       if (hex_document_get_file_size (gh->document) == 0 &&
+                       ! hex_document_has_changed (gh->document))
+       {
+               pango_layout_set_text (layout, " ", -1);
+               goto no_more_lines_to_draw;
+       }
+
+       /* Work out how many lines need to be drawn, and draw them from the
+        * buffer.
+        */
        max_lines = MIN(max_lines, gh->vis_lines);
        max_lines = MIN(max_lines, gh->lines);
 
@@ -952,11 +968,13 @@ render_lines (GtkHex *gh,
                }
        }
 
+no_more_lines_to_draw:
        if (! cursor_drawn)
        {
                DO_RENDER_CURSOR
        }
 }
+#undef DO_RENDER_CURSOR
 
 static void
 render_offsets (GtkHex *gh,