From 2fadd60c0cd87f87a693111abcac03248899f76a Mon Sep 17 00:00:00 2001
From: ole00 <ole00@post.cz>
Date: Sun, 13 Jun 2021 12:36:19 +0200
Subject: [PATCH] implemented grid thickness

Previously the grid point was only one pixel of size. On hi-dpi
screen a single pixel is nearly invisible. This change increases
the grid point size dynamically based on the distance between
grid points.

Signed-off-by: bert <bert.timmerman@xs4all.nl>
---
 src/hid/common/hidgl.c  | 22 +++++++++++++++++++++-
 src/hid/common/hidgl.h  |  2 +-
 src/hid/gtk/gtkhid-gl.c |  2 +-
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/src/hid/common/hidgl.c b/src/hid/common/hidgl.c
index f785f62e..6983902f 100644
--- a/src/hid/common/hidgl.c
+++ b/src/hid/common/hidgl.c
@@ -128,12 +128,15 @@ hidgl_set_depth (float depth)
  * \brief Draw the grid on the 3D canvas
  */
 void
-hidgl_draw_grid (BoxType *drawn_area)
+hidgl_draw_grid (BoxType *drawn_area, double coord_per_px)
 {
   static GLfloat *points = 0;
   static int npoints = 0;
   Coord x1, y1, x2, y2, n, i;
   double x, y;
+  double pixels;
+  double grid_px;
+  double point_size;
 
   if (!Settings.DrawGrid)
     return; /* grid hidden */
@@ -165,6 +168,22 @@ hidgl_draw_grid (BoxType *drawn_area)
       points = realloc (points, npoints * 3 * sizeof (GLfloat));
     }
 
+  pixels = (x2 - x1) / coord_per_px; /* visible grid area in pixels */
+  grid_px = pixels / n; /* distance between grid dots in pixels */
+  point_size = 1.0 + grid_px / 30.0;
+  /* limit the maximum and minimum size of the grid dot - these should really be taken from settings */
+  if (point_size > 4)
+    {
+      point_size = 4;
+    }
+  else if (point_size < 1)
+    {
+      point_size = 1;
+    }
+  /* ensure grid point size is an integer value to prevent moira artefacts */
+  point_size = (int)(point_size + 0.5);
+
+  glPointSize (point_size);
   glEnableClientState (GL_VERTEX_ARRAY);
   glVertexPointer (3, GL_FLOAT, 0, points);
 
@@ -184,6 +203,7 @@ hidgl_draw_grid (BoxType *drawn_area)
     }
 
   glDisableClientState (GL_VERTEX_ARRAY);
+  glPointSize (1);
 }
 
 #define MAX_PIXELS_ARC_TO_CHORD 0.5
diff --git a/src/hid/common/hidgl.h b/src/hid/common/hidgl.h
index 124ba959..9141b064 100644
--- a/src/hid/common/hidgl.h
+++ b/src/hid/common/hidgl.h
@@ -69,7 +69,7 @@ hidgl_add_triangle (triangle_buffer *buffer,
                                  x3, y3, global_depth);
 }
 
-void hidgl_draw_grid (BoxType *drawn_area);
+void hidgl_draw_grid (BoxType *drawn_area, double coord_per_px);
 void hidgl_set_depth (float depth);
 void hidgl_draw_line (int cap, Coord width, Coord x1, Coord y1, Coord x2, Coord y2, double scale);
 void hidgl_draw_arc (Coord width, Coord vx, Coord vy, Coord vrx, Coord vry, Angle start_angle, Angle delta_angle, double scale);
diff --git a/src/hid/gtk/gtkhid-gl.c b/src/hid/gtk/gtkhid-gl.c
index 475fc8a2..4afd99e6 100644
--- a/src/hid/gtk/gtkhid-gl.c
+++ b/src/hid/gtk/gtkhid-gl.c
@@ -233,7 +233,7 @@ ghid_draw_grid (BoxType *drawn_area)
              gport->grid_color.green / 65535.,
              gport->grid_color.blue / 65535.);
 
-  hidgl_draw_grid (drawn_area);
+  hidgl_draw_grid (drawn_area, gport->view.coord_per_px);
 
   glDisable (GL_COLOR_LOGIC_OP);
 }
-- 
2.11.4.GIT