samples: drivers: display: support small displays

With extremely small displays (much smaller than 64x24), the
calculation of the blocks in the four corners fails. These
might then be too large and no longer fit into the available
area of the small displays.

Signed-off-by: Stephan Linz <linz@li-pro.net>

samples/drivers/display/src/main.c

@@ -210,8 +210,17 @@ int main(void)
 		rect_h = 1;
 	}
 
-	h_step = rect_h;
-	scale = (capabilities.x_resolution / 8) / rect_h;
+	if ((capabilities.x_resolution < 3 * rect_w) ||
+	    (capabilities.y_resolution < 3 * rect_h) ||
+	    (capabilities.x_resolution < 8 * rect_h)) {
+		rect_w = capabilities.x_resolution * 40 / 100;
+		rect_h = capabilities.y_resolution * 40 / 100;
+		h_step = capabilities.y_resolution * 20 / 100;
+		scale = 1;
+	} else {
+		h_step = rect_h;
+		scale = (capabilities.x_resolution / 8) / rect_h;
+	}
 
 	rect_w *= scale;
 	rect_h *= scale;