From f19c462c1b1abe493e8e07d20a3232abc5c42517 Mon Sep 17 00:00:00 2001
From: "Adrian A. Baumann" <ade@adebaumann.com>
Date: Tue, 14 Jul 2026 23:28:40 +0200
Subject: [PATCH] Add infinity max option for reciprocal scale

---
 k8s/deployment.yaml      |  2 +-
 web/app.py               | 38 ++++++++++++++++++++++++++++++--------
 web/templates/index.html | 39 +++++++++++++++++++++++++++++++++++++--
 3 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/k8s/deployment.yaml b/k8s/deployment.yaml
index c4f422a..841cef7 100644
--- a/k8s/deployment.yaml
+++ b/k8s/deployment.yaml
@@ -15,7 +15,7 @@ spec:
     spec:
       containers:
         - name: m1730-generator
-          image: git.baumann.gr/adebaumann/m1730-generator:0.82
+          image: git.baumann.gr/adebaumann/m1730-generator:0.83
           imagePullPolicy: Always
           ports:
             - containerPort: 5000
diff --git a/web/app.py b/web/app.py
index d36decc..22cc8e6 100644
--- a/web/app.py
+++ b/web/app.py
@@ -8,7 +8,7 @@ from fontTools.pens.svgPathPen import SVGPathPen
 
 app = Flask(__name__)
 
-VERSION = "0.82"
+VERSION = "0.83"
 
 _LOGO_PATH = pathlib.Path(__file__).parent / 'static' / 'logo.png'
 _LOGO_B64 = base64.b64encode(_LOGO_PATH.read_bytes()).decode()
@@ -291,6 +291,8 @@ def _unit_font_size(unit: str) -> float:
 
 
 def _fmt(v: float) -> str:
+    if math.isinf(v):
+        return '∞'
     # Snap near-integers — log-scale geometric values accumulate FP error
     # (e.g. 9999.9999), which would otherwise miss the integer case.
     r = round(v)
@@ -363,17 +365,31 @@ def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, la
             return min_val + span * (i / big_ticks) ** 2
 
     elif scale_type == 'reciprocal':
-        if min_val <= 0 or max_val <= 0:
+        if min_val <= 0:
             raise ValueError("Reciprocal scale requires min and max values greater than 0.")
-        if max_val <= min_val:
+        if not math.isinf(max_val) and max_val <= min_val:
             raise ValueError("Reciprocal scale requires max value greater than min.")
-        k = 1.0 / min_val - 1.0 / max_val   # always positive
+        if math.isinf(max_val):
+            # Simplified form when max = ∞: x = ZERO_X + SCALE_LEN * min_val / v
+            def value_to_x(v):
+                if math.isinf(v):
+                    return ZERO_X
+                return ZERO_X + SCALE_LEN * min_val / v
 
-        def value_to_x(v):
-            return ZERO_X + SCALE_LEN * (1.0 / v - 1.0 / max_val) / k
+            def major_value(i):
+                if i == 0:
+                    return math.inf
+                return min_val * big_ticks / i
+        else:
+            if max_val <= 0:
+                raise ValueError("Reciprocal scale requires min and max values greater than 0.")
+            k = 1.0 / min_val - 1.0 / max_val   # always positive
 
-        def major_value(i):
-            return 1.0 / (1.0 / max_val + i / big_ticks * k)
+            def value_to_x(v):
+                return ZERO_X + SCALE_LEN * (1.0 / v - 1.0 / max_val) / k
+
+            def major_value(i):
+                return 1.0 / (1.0 / max_val + i / big_ticks * k)
 
     else:
         span = max_val - min_val
@@ -471,6 +487,10 @@ def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, la
             for j in range(1, small_ticks + 1):
                 if scale_type == 'sqrt':
                     x = big_xs[i] + (j / sub) ** 2 * (big_xs[i + 1] - big_xs[i])
+                elif math.isinf(big_vals[i]):
+                    # First interval with ∞ at the left: interpolate in position space
+                    # (linear value interpolation is undefined from ∞).
+                    x = big_xs[i] + (j / sub) * (big_xs[i + 1] - big_xs[i])
                 else:
                     v = big_vals[i] + j * (big_vals[i + 1] - big_vals[i]) / sub
                     x = value_to_x(v)
@@ -511,6 +531,8 @@ def generate():
     label_count = max(2, int(request.form.get('label_count', 6)))
     use_paths   = request.form.get('output_mode', 'paths') == 'paths'
     scale_type  = request.form.get('scale_type', 'linear')
+    if request.form.get('max_is_inf') == '1':
+        max_val = math.inf
 
     custom_labels = [s.strip() for s in request.form.get('labels', '').split(',') if s.strip()] or None
     label_size    = max(0.5, min(25.0, float(request.form.get('label_size', 9))))
diff --git a/web/templates/index.html b/web/templates/index.html
index 5199478..323b000 100644
--- a/web/templates/index.html
+++ b/web/templates/index.html
@@ -330,9 +330,11 @@
             <label>Min value</label>
             <input name="min" type="number" step="any" value="0" required>
           </div>
-          <div class="field">
+          <div class="field" id="field-max">
             <label>Max value</label>
-            <input name="max" type="number" step="any" value="100" required>
+            <input name="max" id="input-max" type="number" step="any" value="100" required>
+            <button type="button" id="btn-inf" style="display:none;font-family:var(--f-mono);font-size:0.65rem;color:var(--muted);background:none;border:none;padding:0;cursor:pointer;text-align:left">set max = ∞</button>
+            <input type="hidden" name="max_is_inf" id="max-is-inf" value="">
           </div>
         </div>
         <input type="hidden" name="scale_type" id="scale-type" value="linear">
@@ -397,6 +399,31 @@
   <script>
     let lastSvg = '';
 
+    function resetInf() {
+      const inp = document.getElementById('input-max');
+      const hidden = document.getElementById('max-is-inf');
+      const btn = document.getElementById('btn-inf');
+      inp.style.display = '';
+      inp.required = true;
+      hidden.value = '';
+      btn.textContent = 'set max = ∞';
+    }
+
+    document.getElementById('btn-inf').addEventListener('click', () => {
+      const inp = document.getElementById('input-max');
+      const hidden = document.getElementById('max-is-inf');
+      const btn = document.getElementById('btn-inf');
+      if (hidden.value === '1') {
+        resetInf();
+      } else {
+        inp.style.display = 'none';
+        inp.required = false;
+        hidden.value = '1';
+        btn.textContent = 'max = ∞ (click to reset)';
+      }
+      doGenerate();
+    });
+
     async function doGenerate() {
       const status = document.getElementById('status');
       status.textContent = 'Generating…';
@@ -448,6 +475,14 @@
               if (!(parseFloat(minInput.value) > 0)) minInput.value = '1';
               if (!(parseFloat(maxInput.value) > parseFloat(minInput.value))) maxInput.value = String(parseFloat(minInput.value) * 10);
             }
+            // Show/hide ∞ toggle
+            const infBtn = document.getElementById('btn-inf');
+            if (btn.dataset.scale === 'reciprocal') {
+              infBtn.style.display = '';
+            } else {
+              infBtn.style.display = 'none';
+              resetInf();
+            }
           }
           doGenerate();
         });