Allow element picker dialog to be moved around

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/615

There is a grab area under the text area, to be used
to move the dialog around.

src/epicker.html

@@ -20,6 +20,14 @@ html#ublock0-epicker,
 #ublock0-epicker div {
     display: block !important;
 }
+#ublock0-epicker #toolbar {
+    cursor: grab;
+    display: flex !important;
+    justify-content: space-between;
+}
+#ublock0-epicker aside.moving #toolbar {
+    cursor: grabbing;
+}
 #ublock0-epicker ul {
     margin: 0.25em 0 0 0 !important;
 }
@@ -31,13 +39,9 @@ html#ublock0-epicker,
     box-shadow: none !important;
     color: #000 !important;
     cursor: pointer !important;
-    margin: 0 0 0 2px !important;
     opacity: 0.7 !important;
     padding: 4px 6px !important;
 }
-#ublock0-epicker button:first-of-type {
-    margin-left: 0 !important;
-}
 #ublock0-epicker button:disabled {
     color: #999 !important;
     background-color: #ccc !important;
@@ -218,12 +222,16 @@ html#ublock0-epicker,
         <textarea lang="en" dir="ltr" spellcheck="false"></textarea>
         <div id="resultsetCount"></div>
     </div>
-    <div><!--
-    --><button id="preview" type="button">{{preview}}</button><!--
-    --><button id="create" type="button" disabled>{{create}}</button><!--
-    --><button id="pick" type="button">{{pick}}</button><!--
-    --><button id="quit" type="button">{{quit}}</button><!--
-    --></div>
+    <div id="toolbar">
+        <div>
+            <button id="preview" type="button">{{preview}}</button>
+        </div>
+        <div>
+            <button id="create" type="button" disabled>{{create}}</button>
+            <button id="pick" type="button">{{pick}}</button>
+            <button id="quit" type="button">{{quit}}</button>
+        </div>
+    </div>
 </section>
 <ul>
     <li id="netFilters">

src/js/scriptlets/element-picker.js

@@ -126,26 +126,26 @@ if (
     return;
 }
 
-var pickerRoot = document.getElementById(vAPI.sessionId);
+let pickerRoot = document.getElementById(vAPI.sessionId);
 if ( pickerRoot ) { return; }
 
-var pickerBody = null;
-var svgOcean = null;
-var svgIslands = null;
-var svgRoot = null;
-var dialog = null;
-var taCandidate = null;
+let pickerBody = null;
+let svgOcean = null;
+let svgIslands = null;
+let svgRoot = null;
+let dialog = null;
+let taCandidate = null;
 
-var netFilterCandidates = [];
-var cosmeticFilterCandidates = [];
+const netFilterCandidates = [];
+const cosmeticFilterCandidates = [];
 
-var targetElements = [];
-var candidateElements = [];
-var bestCandidateFilter = null;
+let targetElements = [];
+let candidateElements = [];
+let bestCandidateFilter = null;
 
-var lastNetFilterSession = window.location.host + window.location.pathname;
-var lastNetFilterHostname = '';
-var lastNetFilterUnion = '';
+const lastNetFilterSession = window.location.host + window.location.pathname;
+let lastNetFilterHostname = '';
+let lastNetFilterUnion = '';
 
 /******************************************************************************/
 
@@ -1517,6 +1517,55 @@ const onScrolled = function() {
 
 /******************************************************************************/
 
+const onStartMoving = (( ) => {
+    let mx0 = 0, my0 = 0;
+    let r0 = 0, b0 = 0;
+    let rMax = 0, bMax = 0;
+
+    const move = ev => {
+        if ( ev.isTrusted === false ) { return; }
+        let r1 = Math.min(Math.max(r0 - ev.pageX + mx0, 4), rMax);
+        let b1 = Math.min(Math.max(b0 - ev.pageY + my0, 4), bMax);
+        dialog.style.setProperty('right', `${r1}px`, 'important');
+        dialog.style.setProperty('bottom', `${b1}px`, 'important');
+        ev.preventDefault();
+        ev.stopPropagation();
+    };
+
+    const stop = ev => {
+        if ( ev.isTrusted === false ) { return; }
+        if ( dialog.classList.contains('moving') === false ) { return; }
+        dialog.classList.remove('moving');
+        const pickerWin = pickerRoot.contentWindow;
+        pickerWin.removeEventListener('mousemove', move, { capture: true });
+        pickerWin.removeEventListener('mouseup', stop, { capture: true, once: true });
+        ev.preventDefault();
+        ev.stopPropagation();
+    };
+
+    return function(ev) {
+        if ( ev.isTrusted === false ) { return; }
+        const target = dialog.querySelector('#toolbar');
+        if ( ev.target !== target ) { return; }
+        if ( dialog.classList.contains('moving') ) { return; }
+        mx0 = ev.pageX; my0 = ev.pageY;
+        const pickerWin = pickerRoot.contentWindow;
+        const style = pickerWin.getComputedStyle(dialog);
+        r0 = parseInt(style.right, 10);
+        b0 = parseInt(style.bottom, 10);
+        const rect = dialog.getBoundingClientRect();
+        rMax = pickerBody.clientWidth - 4 - rect.width ;
+        bMax = pickerBody.clientHeight - 4 - rect.height;
+        dialog.classList.add('moving');
+        pickerWin.addEventListener('mousemove', move, { capture: true });
+        pickerWin.addEventListener('mouseup', stop, { capture: true, once: true });
+        ev.preventDefault();
+        ev.stopPropagation();
+    };
+})();
+
+/******************************************************************************/
+
 const pausePicker = function() {
     pickerBody.classList.add('paused');
     svgListening(false);
@@ -1553,20 +1602,11 @@ const stopPicker = function() {
     vAPI.domFilterer.unexcludeNode(pickerRoot);
 
     window.removeEventListener('scroll', onScrolled, true);
-    pickerRoot.contentWindow.removeEventListener('keydown', onKeyPressed, true);
-    taCandidate.removeEventListener('input', onCandidateChanged);
-    dialog.removeEventListener('click', onDialogClicked);
     svgListening(false);
-    svgRoot.removeEventListener('click', onSvgClicked);
-    svgRoot.removeEventListener('touchstart', onSvgTouchStartStop);
-    svgRoot.removeEventListener('touchend', onSvgTouchStartStop);
     pickerRoot.parentNode.removeChild(pickerRoot);
-    pickerRoot.removeEventListener('load', stopPicker);
-    pickerRoot =
-    pickerBody =
-    dialog =
-    svgRoot = svgOcean = svgIslands =
-    taCandidate = null;
+    pickerRoot = pickerBody =
+        svgRoot = svgOcean = svgIslands =
+        dialog = taCandidate = null;
 
     window.focus();
 };
@@ -1612,6 +1652,8 @@ const startPicker = function(details) {
     taCandidate = dialog.querySelector('textarea');
     taCandidate.addEventListener('input', onCandidateChanged);
 
+    dialog.querySelector('#toolbar').addEventListener('mousedown', onStartMoving);
+
     svgRoot = pickerBody.querySelector('svg');
     svgOcean = svgRoot.firstChild;
     svgIslands = svgRoot.lastChild;