From 1cb8875053eb2815ccb1ce200969ad8f8b6d769c Mon Sep 17 00:00:00 2001
From: XANTRONIX Industrial <xan@xantronix.com>
Date: Sun, 23 Feb 2025 23:45:46 -0500
Subject: [PATCH] Rip out hardcoded isotherms (for now)

---
 lib/xmet/skew_t.py | 42 +++++++++++++-----------------------------
 1 file changed, 13 insertions(+), 29 deletions(-)

diff --git a/lib/xmet/skew_t.py b/lib/xmet/skew_t.py
index 8d66026..a495cf5 100644
--- a/lib/xmet/skew_t.py
+++ b/lib/xmet/skew_t.py
@@ -13,8 +13,12 @@ PRESSURE_LOG_MAX   = math.log(PRESSURE_MAX)
 PRESSURE_LOG_MIN   = math.log(PRESSURE_MIN)
 PRESSURE_LOG_RANGE = PRESSURE_LOG_MAX - PRESSURE_LOG_MIN
 
-TEMP_CENTER = 0 # degrees C
-TEMP_STEP   = 5
+TEMP_MAX        =  60
+TEMP_MIN        = -40
+TEMP_RANGE      = TEMP_MAX - TEMP_MIN
+TEMP_CENTER     =   0 # degrees C
+TEMP_STEP       =   5
+TEMP_STEP_COUNT = 16
 
 def clamp(value, lowest, highest):
     if value < lowest:
@@ -27,25 +31,11 @@ def clamp(value, lowest, highest):
 class SkewT():
     __slots__ = 'width', 'height', 'temp_step_width',
 
-    ISOTHERM_LINES = (
-        (0, 0, 9, 9), (1, 0, 9, 8), (2, 0, 9, 7), (3, 0, 9, 6),
-        (4, 0, 9, 5), (5, 0, 9, 4), (6, 0, 9, 3), (7, 0, 9, 2),
-        (8, 0, 9, 1), (9, 0, 9, 0),
-
-        (-1, 0, 9, 10), (-2, 0, 8, 10), (-3, 0, 7, 10), (-4, 0, 6, 10),
-        (-5, 0, 5, 10), (-6, 0, 4, 10), (-7, 0, 3, 10), (-8, 0, 2, 10),
-        (-9, 0, 1, 10),
-
-        (-9, 1,  0, 10), (-9, 2, -1, 10), (-9, 3, -2, 10), (-9, 4, -3, 10),
-        (-9, 5, -4, 10), (-9, 6, -5, 10), (-9, 7, -6, 10), (-9, 8, -7, 10),
-        (-9, 9, -8, 10),
-    )
-
     def __init__(self, width: float, height: float):
         self.width  = width
         self.height = height
 
-        self.temp_step_width = self.height / 10.0
+        self.temp_step_width = min(self.width, self.height) / TEMP_STEP_COUNT
 
     def graph_to_screen(self, x, y) -> tuple:
         return (self.width / 2) + x, self.height - y
@@ -57,6 +47,8 @@ class SkewT():
         return factor * self.height
 
     def draw_isobars(self, cr: cairo.Context, x: float, y: float):
+        cr.set_source_rgb(0.5, 0.5, 0.5)
+
         for pressure in range(PRESSURE_MIN, PRESSURE_MAX+1, PRESSURE_STEP):
             coord = self.graph_to_screen(-self.width / 2,
                                          self.pressure_y(pressure))
@@ -69,24 +61,16 @@ class SkewT():
     def draw_isotherms(self, cr: cairo.Context, x: float, y: float):
         cr.set_source_rgba(0.1, 0.5, 0.1, 0.8)
 
-        for line in self.ISOTHERM_LINES:
-            x1 = line[0] * self.temp_step_width
-            y1 = line[1] * self.temp_step_width
-            x2 = line[2] * self.temp_step_width
-            y2 = line[3] * self.temp_step_width
+        pass
 
-            (screen_x1, screen_y1) = self.graph_to_screen(x1, y1)
-            (screen_x2, screen_y2) = self.graph_to_screen(x2, y2)
-
-            cr.move_to(x + screen_x1, y + screen_y1)
-            cr.line_to(x + screen_x2, y + screen_y2)
-            cr.stroke()
+    def skew_t_to_graph(self, x: float, y: float):
+        return (x+y, y)
 
     def sample_to_graph(self, temp: float, pressure: float):
         x = (temp / TEMP_STEP) * self.temp_step_width
         y = self.pressure_y(pressure)
 
-        return x + y, y
+        return self.skew_t_to_graph(x, y)
 
     def draw_samples(self,
                      cr: cairo.Context,