From 48d6c3760d3890280ce4308e9d51afe9b281232d Mon Sep 17 00:00:00 2001
From: serxa <sergei@clickhouse.com>
Date: Mon, 6 May 2024 12:05:37 +0000
Subject: [PATCH] workaround for `oklch()` inside canvas bug for firefox

---
 programs/server/dashboard.html | 50 +++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/programs/server/dashboard.html b/programs/server/dashboard.html
index 901211e8ad9..b21d4b86314 100644
--- a/programs/server/dashboard.html
+++ b/programs/server/dashboard.html
@@ -538,9 +538,57 @@ let params = default_params;
 
 /// Palette generation for charts
 function generatePalette(numColors) {
+    // oklch() does not work in firefox<=125 inside <canvas> element so we convert it back to rgb for now.
+    // Based on https://github.com/color-js/color.js/blob/main/src/spaces/oklch.js
+    const multiplyMatrices = (A, B) => {
+        return [
+            A[0]*B[0] + A[1]*B[1] + A[2]*B[2],
+            A[3]*B[0] + A[4]*B[1] + A[5]*B[2],
+            A[6]*B[0] + A[7]*B[1] + A[8]*B[2]
+        ];
+    }
+
+    const oklch2oklab = ([l, c, h]) => [
+        l,
+        isNaN(h) ? 0 : c * Math.cos(h * Math.PI / 180),
+        isNaN(h) ? 0 : c * Math.sin(h * Math.PI / 180)
+    ]
+
+    const srgbLinear2rgb = rgb => rgb.map(c =>
+        Math.abs(c) > 0.0031308 ?
+            (c < 0 ? -1 : 1) * (1.055 * (Math.abs(c) ** (1 / 2.4)) - 0.055) :
+            12.92 * c
+    )
+
+    const oklab2xyz = lab => {
+        const LMSg = multiplyMatrices([
+            1,  0.3963377773761749,  0.2158037573099136,
+            1, -0.1055613458156586, -0.0638541728258133,
+            1, -0.0894841775298119, -1.2914855480194092,
+        ], lab)
+        const LMS = LMSg.map(val => val ** 3)
+        return multiplyMatrices([
+            1.2268798758459243,  -0.5578149944602171,  0.2813910456659647,
+            -0.0405757452148008,  1.1122868032803170, -0.0717110580655164,
+            -0.0763729366746601, -0.4214933324022432,  1.5869240198367816
+        ], LMS)
+    }
+
+    const xyz2rgbLinear = xyz => {
+        return multiplyMatrices([
+            3.2409699419045226,  -1.537383177570094,   -0.4986107602930034,
+           -0.9692436362808796,   1.8759675015077202,   0.04155505740717559,
+            0.05563007969699366, -0.20397695888897652,  1.0569715142428786
+        ], xyz)
+    }
+
+    const oklch2rgb = lch =>  srgbLinear2rgb(xyz2rgbLinear(oklab2xyz(oklch2oklab(lch))))
+
     palette = [];
     for (let i = 0; i < numColors; i++) {
-        palette.push(`oklch(${theme != 'dark' ? 0.75 : 0.5}, 0.15, ${360 * i / numColors})`);
+        //palette.push(`oklch(${theme != 'dark' ? 0.75 : 0.5}, 0.15, ${360 * i / numColors})`);
+        let rgb = oklch2rgb([theme != 'dark' ? 0.75 : 0.5, 0.15, 360 * i / numColors]);
+        palette.push(`rgb(${rgb[0] * 255}, ${rgb[1] * 255}, ${rgb[2] * 255})`);
     }
     return palette;
 }