Add getLineY Layout helper function

openrtx/include/interfaces/graphics.h

@@ -223,6 +223,16 @@ void gfx_drawRect(point_t start, uint16_t width, uint16_t height, color_t color,
  */
 void gfx_drawCircle(point_t start, uint16_t r, color_t color);
 
+/**
+ * Calculates printing position to fit a number of text lines on the screen space.
+ * @param cur: current line number over total (1-based)
+ * @param tot: number of lines to fit in screen
+ * @param startY: starting Y coordinate to leave space for top bar
+ * @param endY: ending Y coordinate to leave space for bottom bar
+ * @return Y coordinates for text printing
+ */
+uint16_t gfx_getLineY(uint8_t cur, uint8_t tot, uint16_t startY, uint16_t endY);
+
 /**
  * Prints text on the screen.
  * @param start: text line start point, in pixel coordinates.

openrtx/src/graphics.c

@@ -385,6 +385,13 @@ static inline uint16_t get_reset_x(textAlign_t alignment, uint16_t line_size,
     return 0;
 }
 
+uint16_t gfx_getLineY(uint8_t cur, uint8_t tot, uint16_t startY, uint16_t endY)
+{
+    // e.g. to print 2 lines we need 3 padding spaces
+    uint16_t step = (endY - startY) / (tot + 1);
+    return startY + (step * cur);
+}
+
 point_t gfx_print(point_t start, fontSize_t size, textAlign_t alignment, 
                   color_t color, const char *fmt, ... )
 {

tests/platform/layout_demo.c

@@ -0,0 +1,53 @@
+/***************************************************************************
+ *   Copyright (C) 2020 by Federico Izzo IU2NUO, Niccolò Izzo IU2KIN and   *
+ *                         Silvano Seva IU2KWO                             *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 3 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, see <http://www.gnu.org/licenses/>   *
+ ***************************************************************************/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <interfaces/graphics.h>
+#include <interfaces/platform.h>
+#include <interfaces/delays.h>
+#include "ui.h"
+
+
+int main(void)
+{
+    platform_init();
+    // Init the graphic stack
+    gfx_init();
+    gfx_clearScreen();
+    gfx_render();
+    platform_setBacklightLevel(255);
+    
+    while(1)
+    {
+        for(int tot=1; tot<=10; tot++)
+        {
+            gfx_clearScreen();
+            for(int cur=1; cur<=tot; cur++)
+            {
+                uint16_t y = gfx_getLineY(cur, tot, 0, SCREEN_HEIGHT);
+                point_t pos = {0, y};
+                gfx_print(pos, FONT_SIZE_8PT, TEXT_ALIGN_CENTER,
+                          color_white, "Line %2d of %2d", cur, tot);
+            }
+            gfx_render();
+            // Sleep for 1 second
+            sleepFor(1u, 0u);
+        }
+    }
+}