write_left,right rounds to pixel. temperature_color robus to nil temp

src/cairo_helpers.lua

@@ -157,12 +157,24 @@ local function text_extents(cr, text)
     return extents
 end
 
+--- Round coordinates to even pixel values
+-- @see https://www.cairographics.org/FAQ/#sharp_lines
+-- @see https://scriptinghelpers.org/questions/4850/how-do-i-round-numbers-in-lua-answered
+-- @tparam cairo_t cr
+-- @number x horizontal pixel coord value
+-- @number y vertical pixel coord value
+local function round_coords(cr, x, y)
+    local u, v = cairo_user_to_device(cr, x, y)
+    return cairo_device_to_user(cr, math.floor(u+0.5), math.floor(v+0.5))
+end
+
 --- Write text left-aligned (to the right of given x).
 -- @tparam cairo_t cr
 -- @number x start of the written text
 -- @number y coordinate of the baseline on top of which the text will be written
 -- @string text
 function ch.write_left(cr, x, y, text)
+    x, y = round_coords(cr, x, y)
     cairo_move_to(cr, x, y)
     cairo_show_text(cr, text)
 end
@@ -173,6 +185,7 @@ end
 -- @number y coordinate of the baseline on top of which the text will be written
 -- @string text
 function ch.write_right(cr, x, y, text)
+    x, y = round_coords(cr, x, y)
     cairo_move_to(cr, x - text_extents(cr, text).width, y)
     cairo_show_text(cr, text)
 end

src/widget.lua

@@ -47,10 +47,16 @@ local temperature_colors = {
 -- @number low threshold for lowest temperature / coolest color
 -- @number high threshold for highest temperature / hottest color
 function w.temperature_color(temperature, low, high)
-    local idx = (temperature - low) / (high - low) * (#temperature_colors - 1) + 1
-    local weight = idx - floor(idx)
-    local cool = temperature_colors[clamp(1, #temperature_colors, floor(idx))]
-    local hot = temperature_colors[clamp(1, #temperature_colors, ceil(idx))]
+    -- defaults in case temperature is nil
+    local cool = temperature_colors[1]
+    local hot = temperature_colors[1]
+    local weight = 0
+    if type(temperature) == "number" and temperature > -math.huge and temperature < math.huge then
+        local idx = (temperature - low) / (high - low) * (#temperature_colors - 1) + 1
+        weight = idx - floor(idx)
+        cool = temperature_colors[clamp(1, #temperature_colors, floor(idx))]
+        hot = temperature_colors[clamp(1, #temperature_colors, ceil(idx))]
+    end
     return cool[1] + weight * (hot[1] - cool[1]),
            cool[2] + weight * (hot[2] - cool[2]),
            cool[3] + weight * (hot[3] - cool[3])