Paint navigation arrows in SHOW

This improves the UX in the SHOW command as it indicates to the user
that there are more grob to paint in the corresponding direction
pointed by the arrows.

Authored-by: Jesus Cano <[email protected]>
Reviewed-by: Christophe de Dinechin <[email protected]>

Author: jpcano

src/graphics.cc

@@ -1152,6 +1152,88 @@ static coord show_x       = 0;
 static coord show_y       = 0;
 static coord show_delta   = 8;
 
+static void draw_show_horizontal_arrow(coord tipx, coord tipy,
+                                       coord size, coord padding,
+                                       bool right, pattern fc, pattern bc)
+// ----------------------------------------------------------------------------
+//   Draw a left/right pointing arrow with tip at (tipx, tipy)
+// ----------------------------------------------------------------------------
+//   tipx, tipy: Arrow tip coordinates on screen (assuming the padding is 0)
+//   size:       Arrow size in pixels
+//   padding:    Extra pixels around the arrow body
+//   right:      true for a right arrow, false for a left arrow
+//   fc:         Foreground pattern for the arrow
+//   bc:         Background pattern behind the arrow
+{
+    Screen.fill(right ? tipx - size - 2*padding: tipx,
+                tipy - size - padding,
+                right ? tipx : tipx + size + 2*padding,
+                tipy + size + padding,
+                bc);
+    for (coord offset = 0; offset < size; offset++)
+    {
+        coord span = offset + 1;
+        coord x = right ? tipx - offset - padding : tipx + offset + padding;
+        Screen.fill(x, tipy - span + 1, x, tipy + span - 1, fc);
+    }
+}
+
+
+
+static void draw_show_vertical_arrow(coord tipx, coord tipy,
+                                     coord size, coord padding,
+                                     bool down, pattern fc, pattern bc)
+// ----------------------------------------------------------------------------
+//   Draw an up/down pointing arrow with tip at (tipx, tipy)
+// ----------------------------------------------------------------------------
+//   tipx, tipy: Arrow tip coordinates on screen (assuming padding is 0)
+//   size:       Arrow size in pixels
+//   padding:    Extra pixels around the arrow body
+//   down:       true for a down arrow, false for an up arrow
+//   fc:         Foreground pattern for the arrow
+//   bc:         Background pattern behind the arrow
+{
+    Screen.fill(tipx - size - padding,
+                down ? tipy - size - 2*padding : tipy,
+                tipx + size + padding,
+                down ? tipy : tipy + size + 2*padding,
+                bc);
+    for (coord offset = 0; offset < size; offset++)
+    {
+        coord span = offset + 1;
+        coord y = down ? tipy - offset - padding : tipy + offset + padding;
+        Screen.fill(tipx - span + 1, y, tipx + span - 1, y, fc);
+    }
+}
+
+
+static void draw_show_arrows(grob::pixsize width, grob::pixsize height)
+// ----------------------------------------------------------------------------
+//   Render navigation arrows if the grob object is bigger than the display
+// ----------------------------------------------------------------------------
+//   width, height: Size of the full grob being shown
+{
+    auto        fc            = Settings.Foreground();
+    auto        bc            = pattern::gray90;
+    const coord arrow_size    = 6;
+    const coord arrow_padding = 2;
+    coord       midx          = LCD_W / 2;
+    coord       midy          = LCD_H / 2;
+
+    if (show_x > 0)
+        draw_show_horizontal_arrow(0, midy, arrow_size, arrow_padding,
+                                   false, fc, bc);
+    if (show_x + LCD_W < coord(width))
+        draw_show_horizontal_arrow(LCD_W - 1, midy, arrow_size, arrow_padding,
+                                   true, fc, bc);
+    if (show_y > 0)
+        draw_show_vertical_arrow(midx, 0, arrow_size, arrow_padding,
+                                 false, fc, bc);
+    if (show_y + LCD_H < coord(height))
+        draw_show_vertical_arrow(midx, LCD_H - 1, arrow_size, arrow_padding,
+                                 true, fc, bc);
+}
+
 
 void show_grob(grob_p graph)
 // ----------------------------------------------------------------------------
@@ -1179,6 +1261,7 @@ void show_grob(grob_p graph)
         grob::surface s = graph->pixels();
         Screen.copy(s, r, point(show_x,show_y));
     }
+    draw_show_arrows(width, height);
     mark_dirty(0, 0, LCD_W-1, LCD_H-1);
     refresh_dirty();
 }