Implement SkewTOptions class

Implement SkewTOptions class to allow specifying exact items to be
rendered on a Skew-T chart

lib/xmet/skew_t.py

@@ -21,7 +21,7 @@ TEMP_CENTER     =   0 # degrees C
 TEMP_STEP       =   5
 TEMP_STEP_COUNT = math.ceil(TEMP_RANGE / TEMP_STEP)
 
-SKEW = 1.0
+SKEW_DEFAULT = 1.0
 
 def clamp(value, lowest, highest):
     if value < lowest:
@@ -31,13 +31,25 @@ def clamp(value, lowest, highest):
 
     return value
 
-class SkewTGraph():
+class SkewTOptions():
-    __slots__ = 'width', 'height', 'skew', 'temp_step_width',
+    def __init__(self):
+        self.skew                = SKEW_DEFAULT
+        self.draw_dry_adiabats       = True
+        self.draw_moist_adiabats     = True
+        self.draw_lcl                = False
+        self.draw_lfc                = False
+        self.draw_el                 = False
+        self.draw_cape_mixing_ratio  = False
+        self.draw_cape_dry_adiabat   = False
+        self.draw_cape_moist_adiabat = False
 
-    def __init__(self, width: float, height: float, skew: float=SKEW):
+class SkewTGraph():
+    __slots__ = 'width', 'height', 'opts', 'temp_step_width',
+
+    def __init__(self, width: float, height: float, opts: SkewTOptions=SkewTOptions()):
         self.width  = width
         self.height = height
-        self.skew   = skew
+        self.opts   = opts
 
         self.temp_step_width = min(self.width, self.height) / TEMP_STEP_COUNT
 
@@ -75,7 +87,7 @@ class SkewTGraph():
         cr.restore()
 
     def skew_t_to_graph(self, x: float, y: float):
-        return (x+self.skew*y, y)
+        return (x+self.opts.skew*y, y)
 
     def sample_to_graph(self, temp: float, pressure: float):
         x = (temp / TEMP_STEP) * self.temp_step_width
@@ -137,15 +149,17 @@ class SkewTGraph():
                       y: float):
         cr.save()
 
-        cr.set_source_rgba(1.0, 0.2, 0, 0.2)
+        if self.opts.draw_dry_adiabats:
+            cr.set_source_rgba(1.0, 0.2, 0, 0.2)
 
-        for temp in range(-140, 140, 10):
+            for temp in range(-160, 160, 10):
-            self.draw_adiabat(cr, x, y, temp, 1000.0, lambda t, p: LAPSE_RATE_DRY)
+                self.draw_adiabat(cr, x, y, temp, 1000.0, lambda t, p: LAPSE_RATE_DRY)
 
-        cr.set_source_rgba(0.3, 0.1, 0, 0.2)
+        if self.opts.draw_moist_adiabats:
+            cr.set_source_rgba(0.3, 0.1, 0, 0.2)
 
-        for temp in range(-140, 140, 5):
+            for temp in range(-140, 140, 5):
-            self.draw_adiabat(cr, x, y, temp, 1000.0, moist_lapse_rate)
+                self.draw_adiabat(cr, x, y, temp, 1000.0, moist_lapse_rate)
 
         cr.restore()
 
@@ -219,6 +233,32 @@ class SkewTGraph():
         self.draw_isobars(cr, x, y)
         self.draw_adiabats(cr, x, y)
 
+        params = SoundingParameters.from_sounding(sounding)
+
+        if self.opts.draw_lcl:
+            cr.set_source_rgb(1.0, 0.4, 0.0)
+            self.draw_isobar(cr, x, y, params.lcl[1])
+
+        if self.opts.draw_lfc:
+            cr.set_source_rgb(1.0, 0.4, 0.0)
+            self.draw_isobar(cr, x, y, params.lfc[1])
+
+        if self.opts.draw_el:
+            cr.set_source_rgb(1.0, 0.4, 0.0)
+            self.draw_isobar(cr, x, y, params.el[1])
+
+        if self.opts.draw_cape_dry_adiabat:
+            cr.set_source_rgb(1.0, 0.8, 0.2)
+            self.draw_series(cr, x, y, params.dry_adiabat)
+
+        if self.opts.draw_cape_moist_adiabat:
+            cr.set_source_rgb(0.8, 0.5, 0.8)
+            self.draw_series(cr, x, y, params.moist_adiabat)
+
+        if self.opts.draw_cape_mixing_ratio:
+            cr.set_source_rgb(0.8, 0.8, 1.0)
+            self.draw_series(cr, x, y, params.saturated_mr_line)
+
         cr.set_source_rgb(1, 0, 0)
         self.draw_sounding(cr, x, y, sounding, lambda s: s.temp)
 
@@ -242,7 +282,7 @@ class SkewTLegend():
             x_rel, y_rel = skew_t.sample_to_screen(temp, PRESSURE_MAX)
 
             if x_rel < 0:
-                y_rel = skew_t.height + x_rel / skew_t.skew
+                y_rel = skew_t.height + x_rel / skew_t.opts.skew
                 x_rel = 0
 
                 if y_rel <= 0: