BarChart: fix crash when checking bar value text overlap (#52061)

public/app/plugins/panel/barchart/bars.ts

@@ -250,7 +250,7 @@ export function getConfig(opts: BarsOptions, theme: GrafanaTheme2) {
   let barsPctLayout: Array<null | { offs: number[]; size: number[] }> = [];
   let barsColors: Array<null | { fill: Array<string | null>; stroke: Array<string | null> }> = [];
   let scaleFactor = 1;
-  let labels: ValueLabelTable = {};
+  let labels: ValueLabelTable;
   let fontSize = opts.text?.valueSize ?? VALUE_MAX_FONT_SIZE;
   let labelOffset = LABEL_OFFSET_MAX;
 
@@ -512,8 +512,12 @@ export function getConfig(opts: BarsOptions, theme: GrafanaTheme2) {
       curBaseline: CanvasTextBaseline | undefined = undefined;
 
     for (const didx in labels) {
+      // exclude first label from overlap testing
+      let first = true;
+
       for (const sidx in labels[didx]) {
-        const { text, value, x = 0, y = 0, bbox = { x: 0, y: 0, w: 1, h: 1 } } = labels[didx][sidx];
+        const label = labels[didx][sidx];
+        const { text, value, x = 0, y = 0 } = label;
 
         let align: CanvasTextAlign = isXHorizontal ? 'center' : value !== null && value < 0 ? 'right' : 'left';
         let baseline: CanvasTextBaseline = isXHorizontal
@@ -533,19 +537,33 @@ export function getConfig(opts: BarsOptions, theme: GrafanaTheme2) {
         if (showValue === VisibilityMode.Always) {
           u.ctx.fillText(text, x, y);
         } else if (showValue === VisibilityMode.Auto) {
-          let intersectsLabel = false;
+          let { bbox } = label;
 
-          // Test for any collisions
-          for (const subsidx in labels[didx]) {
-            const r = labels[didx][subsidx].bbox!;
+          let intersectsLabel = false;
 
-            if (!labels[didx][subsidx].hidden && sidx !== subsidx && intersects(bbox, r)) {
-              intersectsLabel = true;
-              labels[didx][sidx].hidden = true;
-              break;
+          if (bbox == null) {
+            intersectsLabel = true;
+            label.hidden = true;
+          } else if (!first) {
+            // Test for any collisions
+            for (const subsidx in labels[didx]) {
+              if (subsidx === sidx) {
+                continue;
+              }
+
+              const label2 = labels[didx][subsidx];
+              const { bbox: bbox2, hidden } = label2;
+
+              if (!hidden && bbox2 && intersects(bbox, bbox2)) {
+                intersectsLabel = true;
+                label.hidden = true;
+                break;
+              }
             }
           }
 
+          first = false;
+
           !intersectsLabel && u.ctx.fillText(text, x, y);
         }
       }