fix(scaleColumns): adjust for overflow when scaling columns in flex mode (#43)

* fix(scaleColumns): adjust for overflow when scaling columns in flex mode

* fix(scaleColumns): handle null pointer for biggest column ref

* fix(scaleColumns): respect min widths when applying fixes

Author: peter-stoyanov

projects/ngx-datatable/src/lib/utils/math.spec.ts

@@ -1,4 +1,4 @@
-import { forceFillColumnWidths } from './math';
+import { adjustColumnWidths, forceFillColumnWidths } from './math';
 
 describe('Math function', () => {
   describe('forceFillColumnWidths', () => {
@@ -34,4 +34,51 @@ describe('Math function', () => {
       });
     });
   });
+
+  describe('adjustColumnWidths', () => {
+    describe('flex mode', () => {
+      it('should not go over/under compared to given max width', () => {
+        const cols = [
+          { prop: 'id1', width: 287, maxWidth: undefined, minWidth: 175, flexGrow: 2, canAutoResize: true },
+          { prop: 'id2', width: 215, maxWidth: undefined, minWidth: 200, flexGrow: 1.5, canAutoResize: true },
+          { prop: 'id3', width: 287, maxWidth: undefined, minWidth: 150, flexGrow: 2, canAutoResize: true },
+          { prop: 'id4', width: 175, maxWidth: undefined, minWidth: 175, flexGrow: 1, canAutoResize: true },
+          { prop: 'id5', width: 143, maxWidth: undefined, minWidth: 120, flexGrow: 1, canAutoResize: true }
+        ];
+
+        const givenTableWidth = 1180;
+
+        adjustColumnWidths(cols, givenTableWidth);
+
+        const totalAdjustedColumnWidths = cols.map(c => c.width).reduce((p, c) => p + c, 0);
+        expect(totalAdjustedColumnWidths).toBeCloseTo(givenTableWidth, 0.001);
+      });
+
+      it('should overflow if the total of given min widths is bigger than given max width', () => {
+        const cols = [
+          { prop: 'id1', width: 100, maxWidth: undefined, minWidth: 100, flexGrow: 1, canAutoResize: true },
+          { prop: 'id2', width: 100, maxWidth: undefined, minWidth: 100, flexGrow: 1, canAutoResize: true }
+        ];
+        const maxWidth = 199;
+
+        adjustColumnWidths(cols, maxWidth);
+
+        const totalAdjustedColumnWidths = cols.map(c => c.width).reduce((p, c) => p + c, 0);
+        expect(totalAdjustedColumnWidths).toBeGreaterThan(maxWidth);
+      });
+
+      it('should respect min widths', () => {
+        const cols = [
+          { prop: 'id1', width: 0, maxWidth: undefined, minWidth: 10, flexGrow: 3.0000000000000075, canAutoResize: true },
+          { prop: 'id2', width: 0, maxWidth: undefined, minWidth: 10, flexGrow: 1, canAutoResize: true }
+        ];
+
+        adjustColumnWidths(cols, 40);
+
+        for (const col of cols) {
+          expect(col.width - col.minWidth).toBeGreaterThanOrEqual(0);
+        }
+      });
+    });
+  });
 });

projects/ngx-datatable/src/lib/utils/math.ts

@@ -31,9 +31,9 @@ export function adjustColumnWidths(allColumns: any, expectedWidth: any) {
  * Resizes columns based on the flexGrow property, while respecting manually set widths
  */
 function scaleColumns(colsByGroup: any, maxWidth: any, totalFlexGrow: any) {
-  // calculate total width and flexgrow points for coulumns that can be resized
+  // calculate total width and flexgrow points for columns that can be resized
   for (const attr in colsByGroup) {
-    if (colsByGroup.hasOwnProperty(attr)){
+    if (colsByGroup.hasOwnProperty(attr)) {
       for (const column of colsByGroup[attr]) {
         if (column.$$oldWidth) {
           // when manually resized, switch off auto-resize
@@ -58,9 +58,9 @@ function scaleColumns(colsByGroup: any, maxWidth: any, totalFlexGrow: any) {
     remainingWidth = 0;
 
     for (const attr in colsByGroup) {
-      if (colsByGroup.hasOwnProperty(attr)){
+      if (colsByGroup.hasOwnProperty(attr)) {
         for (const column of colsByGroup[attr]) {
-        // if the column can be resize and it hasn't reached its minimum width yet
+          // if the column can be resize and it hasn't reached its minimum width yet
           if (column.canAutoResize && !hasMinWidth[column.prop]) {
             const newWidth = column.width + column.flexGrow * widthPerFlexPoint;
             if (column.minWidth !== undefined && newWidth < column.minWidth) {
@@ -75,6 +75,32 @@ function scaleColumns(colsByGroup: any, maxWidth: any, totalFlexGrow: any) {
       }
     }
   } while (remainingWidth !== 0);
+
+  // Adjust for any remaining offset in computed widths vs maxWidth
+  const columns = Object.values<{
+    width: number,
+    canAutoResize: boolean,
+    minWidth: number,
+    maxWidth: number
+  }>(colsByGroup).reduce((acc, col) => acc.concat(col), []);
+
+  const totalWidthAchieved = columns.reduce((acc, col) => acc + col.width, 0);
+  const delta = maxWidth - totalWidthAchieved;
+
+  if (delta === 0) {
+    return
+  }
+
+  // adjust the first column that can be auto-resized respecting the min/max widths
+  for (const col of columns.filter(c => c.canAutoResize).sort((a, b) => a.width - b.width)) {
+    if (
+      (delta > 0 && (!col.maxWidth || col.width + delta <= col.maxWidth)) ||
+      (delta < 0 && (!col.minWidth || col.width + delta >= col.minWidth))
+    ) {
+      col.width += delta;
+      break;
+    }
+  }
 }
 
 /**