Merge pull request #4630 from caugner/feature-preserve-cursor-in-editor-upload

FEATURE: Preserve cursor in editor upload

app/assets/javascripts/discourse/components/d-editor.js.es6

@@ -12,6 +12,7 @@ import { emojiSearch } from 'pretty-text/emoji';
 import { emojiUrlFor } from 'discourse/lib/text';
 import { getRegister } from 'discourse-common/lib/get-owner';
 import { findRawTemplate } from 'discourse/lib/raw-templates';
+import { determinePostReplaceSelection } from 'discourse/lib/utilities';
 import deprecated from 'discourse-common/lib/deprecated';
 
 // Our head can be a static string or a function that returns a string
@@ -525,11 +526,27 @@ export default Ember.Component.extend({
 
   _replaceText(oldVal, newVal) {
     const val = this.get('value');
-    const loc = val.indexOf(oldVal);
-    if (loc !== -1) {
-      this.set('value', val.replace(oldVal, newVal));
-      this._selectText(loc + newVal.length, 0);
+    const needleStart = val.indexOf(oldVal);
+
+    if (needleStart === -1) {
+      // Nothing to replace.
+      return;
     }
+
+    const textarea = this.$('textarea.d-editor-input')[0];
+
+    // Determine post-replace selection.
+    const newSelection = determinePostReplaceSelection({
+      selection: { start: textarea.selectionStart, end: textarea.selectionEnd },
+      needle: { start: needleStart, end: needleStart + oldVal.length },
+      replacement: { start: needleStart, end: needleStart + newVal.length }
+    });
+
+    // Replace value (side effect: cursor at the end).
+    this.set('value', val.replace(oldVal, newVal));
+
+    // Restore cursor.
+    this._selectText(newSelection.start, newSelection.end - newSelection.start);
   },
 
   _addText(sel, text) {

app/assets/javascripts/discourse/lib/utilities.js.es6

@@ -300,5 +300,35 @@ export function defaultHomepage() {
   return Discourse.SiteSettings.top_menu.split("|")[0].split(",")[0];
 }
 
+export function determinePostReplaceSelection({ selection, needle, replacement }) {
+  const diff = (replacement.end - replacement.start) - (needle.end - needle.start);
+
+  if (selection.end <= needle.start) {
+    // Selection ends (and starts) before needle.
+    return { start: selection.start, end: selection.end };
+  } else if (selection.start <= needle.start) {
+    // Selection starts before needle...
+    if (selection.end < needle.end) {
+      // ... and ends inside needle.
+      return { start: selection.start, end: needle.start };
+    } else {
+      // ... and spans needle completely.
+      return { start: selection.start, end: selection.end + diff };
+    }
+  } else if (selection.start < needle.end) {
+    // Selection starts inside needle...
+    if (selection.end <= needle.end) {
+      // ... and ends inside needle.
+      return { start: replacement.end, end: replacement.end };
+    } else {
+      // ... and spans end of needle.
+      return { start: replacement.end, end: selection.end + diff };
+    }
+  } else {
+    // Selection starts (and ends) behind needle.
+    return { start: selection.start + diff, end: selection.end + diff };
+  }
+}
+
 // This prevents a mini racer crash
 export default {};

test/javascripts/components/d-editor-test.js.es6

@@ -760,7 +760,7 @@ componentTest('emoji', {
   }
 });
 
-testCase("replace-text event", function(assert, textarea) {
+testCase("replace-text event", function(assert) {
 
   this.set('value', "red green blue");
 
@@ -770,7 +770,96 @@ testCase("replace-text event", function(assert, textarea) {
 
   andThen(() => {
     assert.equal(this.get('value'), 'red yellow blue');
-    assert.equal(textarea.selectionStart, 10);
-    assert.equal(textarea.selectionEnd, 10);
   });
 });
+
+(() => {
+  // Tests to check cursor/selection after replace-text event.
+  const BEFORE = 'red green blue';
+  const NEEDLE = 'green';
+  const REPLACE = 'yellow';
+  const AFTER = BEFORE.replace(NEEDLE, REPLACE);
+
+  const CASES = [
+    {
+      description: 'cursor at start remains there',
+      before: [0, 0],
+      after: [0, 0]
+    },{
+      description: 'cursor before needle becomes cursor before replacement',
+      before: [BEFORE.indexOf(NEEDLE), 0],
+      after: [AFTER.indexOf(REPLACE), 0]
+    },{
+      description: 'cursor at needle start + 1 moves behind replacement',
+      before: [BEFORE.indexOf(NEEDLE) + 1, 0],
+      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 0]
+    },{
+      description: 'cursor at needle end - 1 stays behind replacement',
+      before: [BEFORE.indexOf(NEEDLE) + NEEDLE.length - 1, 0],
+      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 0]
+    },{
+      description: 'cursor behind needle becomes cursor behind replacement',
+      before: [BEFORE.indexOf(NEEDLE) + NEEDLE.length, 0],
+      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 0]
+    },{
+      description: 'cursor at end remains there',
+      before: [BEFORE.length, 0],
+      after: [AFTER.length, 0]
+    },{
+      description: 'selection spanning needle start becomes selection until replacement start',
+      before: [BEFORE.indexOf(NEEDLE) - 1, 2],
+      after: [AFTER.indexOf(REPLACE) - 1, 1]
+    },{
+      description: 'selection spanning needle end becomes selection from replacement end',
+      before: [BEFORE.indexOf(NEEDLE) + NEEDLE.length - 1, 2],
+      after: [AFTER.indexOf(REPLACE) + REPLACE.length, 1]
+    },{
+      description: 'selection spanning needle becomes selection spanning replacement',
+      before: [BEFORE.indexOf(NEEDLE) - 1, NEEDLE.length + 2],
+      after: [AFTER.indexOf(REPLACE) - 1, REPLACE.length + 2]
+    },{
+      description: 'complete selection remains complete',
+      before: [0, BEFORE.length],
+      after: [0, AFTER.length]
+    }
+  ];
+
+  function setSelection(textarea, [start, len]) {
+    textarea.selectionStart = start;
+    textarea.selectionEnd = start + len;
+  }
+
+  function getSelection(textarea) {
+    const start = textarea.selectionStart;
+    const end = textarea.selectionEnd;
+    return [start, end - start];
+  }
+
+  function formatTextWithSelection(text, [start, len]) {
+    return [
+      '"',
+      text.substr(0, start),
+      '<',
+      text.substr(start, len),
+      '>',
+      text.substr(start+len),
+      '"',
+    ].join('');
+  }
+
+  for (let i = 0; i < CASES.length; i++) {
+    const CASE = CASES[i];
+    testCase(`replace-text event: ${CASE.description}`, function(assert, textarea) {
+      this.set('value', BEFORE);
+      setSelection(textarea, CASE.before);
+      andThen(() => {
+        this.container.lookup('app-events:main').trigger('composer:replace-text', 'green', 'yellow');
+      });
+      andThen(() => {
+        let expect = formatTextWithSelection(AFTER, CASE.after);
+        let actual = formatTextWithSelection(this.get('value'), getSelection(textarea));
+        assert.equal(actual, expect);
+      });
+    });
+  }
+})();