refactor(ui): share Bresenham line + midpoint circle in GfxUtils.h

drawLine was duplicated verbatim in TrailScreen and CompassScreen, and
drawCircle lived only in CompassScreen. Lift both into a gfx:: namespace
header so the map and compass share one copy of each 1-px primitive.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/companion_radio/ui-new/CompassScreen.h

@@ -8,6 +8,7 @@
 // being recorded.
 
 #include "../GeoUtils.h"
+#include "GfxUtils.h"
 #include <math.h>
 
 class CompassScreen : public UIScreen {
@@ -15,33 +16,6 @@ class CompassScreen : public UIScreen {
 
   bool gpsValid() const { int32_t lat, lon; return _task->currentLocation(lat, lon); }
 
-  // Midpoint circle (DisplayDriver has no circle primitive).
-  static void drawCircle(DisplayDriver& d, int cx, int cy, int r) {
-    int x = r, y = 0, err = 1 - r;
-    while (x >= y) {
-      d.fillRect(cx + x, cy + y, 1, 1); d.fillRect(cx + y, cy + x, 1, 1);
-      d.fillRect(cx - y, cy + x, 1, 1); d.fillRect(cx - x, cy + y, 1, 1);
-      d.fillRect(cx - x, cy - y, 1, 1); d.fillRect(cx - y, cy - x, 1, 1);
-      d.fillRect(cx + y, cy - x, 1, 1); d.fillRect(cx + x, cy - y, 1, 1);
-      y++;
-      if (err < 0) err += 2 * y + 1;
-      else { x--; err += 2 * (y - x) + 1; }
-    }
-  }
-
-  static void drawLine(DisplayDriver& d, int x0, int y0, int x1, int y1) {
-    int dx = abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
-    int dy = -abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
-    int err = dx + dy;
-    while (true) {
-      d.fillRect(x0, y0, 1, 1);
-      if (x0 == x1 && y0 == y1) break;
-      int e2 = err * 2;
-      if (e2 >= dy) { err += dy; x0 += sx; }
-      if (e2 <= dx) { err += dx; y0 += sy; }
-    }
-  }
-
 public:
   CompassScreen(UITask* task) : _task(task) {}
   void enter() {}
@@ -74,7 +48,7 @@ public:
     int cog;
     bool have = _task->currentCourse(cog);
 
-    drawCircle(display, cx, cy, r);   // compass ring
+    gfx::drawCircle(display, cx, cy, r);   // compass ring
 
     // Fixed forward index at the top: the direction you are travelling is
     // always "up". The compass card (North) rotates underneath it.
@@ -98,11 +72,11 @@ public:
 
     // North needle from centre.
     int nx, ny; cardPos(0, r - 2, nx, ny);
-    drawLine(display, cx, cy, nx, ny);
+    gfx::drawLine(display, cx, cy, nx, ny);
     float nrad = (0 - cog) * (float)M_PI / 180.0f;
     for (int da = -25; da <= 25; da += 50) {
       float a = nrad + (float)M_PI + da * (float)M_PI / 180.0f;
-      drawLine(display, nx, ny, nx + (int)(sinf(a) * 4), ny - (int)(cosf(a) * 4));
+      gfx::drawLine(display, nx, ny, nx + (int)(sinf(a) * 4), ny - (int)(cosf(a) * 4));
     }
 
     // Cardinal letters around the rim (N at the needle tip).

examples/companion_radio/ui-new/GfxUtils.h

@@ -0,0 +1,40 @@
+#pragma once
+// Small 1-px drawing primitives the DisplayDriver abstraction doesn't provide
+// (no line / circle in the GFX wrapper used here). Shared by the map and the
+// compass so the Bresenham / midpoint routines aren't copy-pasted per screen.
+// Everything is plotted as 1x1 fillRect to stay within DisplayDriver's API.
+
+#include <helpers/ui/DisplayDriver.h>
+#include <stdlib.h>   // abs
+
+namespace gfx {
+
+// Bresenham line between two points.
+static inline void drawLine(DisplayDriver& d, int x0, int y0, int x1, int y1) {
+  int dx =  abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
+  int dy = -abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
+  int err = dx + dy;
+  while (true) {
+    d.fillRect(x0, y0, 1, 1);
+    if (x0 == x1 && y0 == y1) break;
+    int e2 = err * 2;
+    if (e2 >= dy) { err += dy; x0 += sx; }
+    if (e2 <= dx) { err += dx; y0 += sy; }
+  }
+}
+
+// Midpoint-circle outline.
+static inline void drawCircle(DisplayDriver& d, int cx, int cy, int r) {
+  int x = r, y = 0, err = 1 - r;
+  while (x >= y) {
+    d.fillRect(cx + x, cy + y, 1, 1); d.fillRect(cx + y, cy + x, 1, 1);
+    d.fillRect(cx - y, cy + x, 1, 1); d.fillRect(cx - x, cy + y, 1, 1);
+    d.fillRect(cx - x, cy - y, 1, 1); d.fillRect(cx - y, cy - x, 1, 1);
+    d.fillRect(cx + y, cy - x, 1, 1); d.fillRect(cx + x, cy - y, 1, 1);
+    y++;
+    if (err < 0) err += 2 * y + 1;
+    else { x--; err += 2 * (y - x) + 1; }
+  }
+}
+
+}  // namespace gfx

examples/companion_radio/ui-new/TrailScreen.h

@@ -7,6 +7,7 @@
 
 #include "../Trail.h"
 #include "../GeoUtils.h"
+#include "GfxUtils.h"
 #include "NavView.h"
 #include <math.h>
 
@@ -733,7 +734,7 @@ private:
           drawFilledDot(display, x0, y0);
           drawOpenDot(display, x1, y1);
         } else {
-          drawLine(display, x0, y0, x1, y1);
+          gfx::drawLine(display, x0, y0, x1, y1);
         }
         x0 = x1;
         y0 = y1;
@@ -882,19 +883,6 @@ private:
     display.print(lbl);
   }
 
-  static void drawLine(DisplayDriver& d, int x0, int y0, int x1, int y1) {
-    int dx =  abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
-    int dy = -abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
-    int err = dx + dy;
-    while (true) {
-      d.fillRect(x0, y0, 1, 1);
-      if (x0 == x1 && y0 == y1) break;
-      int e2 = err * 2;
-      if (e2 >= dy) { err += dy; x0 += sx; }
-      if (e2 <= dx) { err += dx; y0 += sy; }
-    }
-  }
-
   static void drawFilledDot(DisplayDriver& d, int cx, int cy) {
     d.fillRect(cx - 1, cy - 1, 3, 3);
   }