glcanon: add a way to prevent cone scaling with loaded G-code extents

Useful on larger machines (like routers or plasma tables), especially without traditional "tools" where the user does not want a giant cone for a large G-code file.

Author: snowgoer540

docs/src/config/ini-config.adoc

@@ -250,7 +250,8 @@ Descriptions of the interfaces are in the Interfaces section of the User Manual.
   The example above will display only one decimal digit.
   Formatting follows Python practice: https://docs.python.org/2/library/string.html#format-specification-mini-language .
   An error will be raised if the format can not accept a floating-point value.
-* `CONE_BASESIZE = .25` - Override the default cone/tool base size of .5 in the graphics display.
+* `CONE_BASESIZE = .25` - Override the default cone/tool base size of .5 in the graphics display. Valid values are between 0.025 and 2.0.
+* `DISABLE_CONE_SCALING = TRUE` - Any non-empty value (including "0") will override the default behavior of scaling the cone/tool size using the extents of the currently loaded G-code program in the graphics display.
 * `MAX_FEED_OVERRIDE = 1.2` - The maximum feed override the user may select.
   1.2 means 120% of the programmed feed rate.
 * `MIN_SPINDLE_OVERRIDE = 0.5` - The minimum spindle override the user may select.

lib/python/rs274/glcanon.py

@@ -517,6 +517,7 @@ def __init__(self, s=None, lp=None, g=None):
         self.foam_w_height = 1.5
         self.foam_z_height = 0
         self.hide_icons = False
+        self.disable_cone_scaling = False
 
         try:
             system_memory_bytes = os.sysconf('SC_PAGE_SIZE') * os.sysconf('SC_PHYS_PAGES')
@@ -565,6 +566,8 @@ def __init__(self, s=None, lp=None, g=None):
                 if not temp is None:
                     self.max_file_size = int(temp) * 1024 * 1024
 
+                self.disable_cone_scaling = bool(self.inifile.find("DISPLAY", "DISABLE_CONE_SCALING"))
+
         except:
             # Probably started in an editor so no INI
             pass
@@ -640,7 +643,7 @@ def select(self, x_view, y_view):
         if self.get_show_rapids():
             glCallList(self.dlist('select_rapids', gen=self.make_selection_list))
         glCallList(self.dlist('select_norapids', gen=self.make_selection_list))
-        
+
         try:
             buffer = glRenderMode(GL_RENDER)
         except:
@@ -1494,7 +1497,7 @@ def redraw(self):
 
                 current_tool = self.get_current_tool()
                 if current_tool is None or current_tool.diameter == 0:
-                    if self.canon:
+                    if self.canon and not self.disable_cone_scaling:
                         g = self.canon
 
                         cone_scale = max(g.max_extents[X] - g.min_extents[X],