function onMouseDown()

in lib/ace/mouse/multi_select_handler.js [41:198]


function onMouseDown(e) {
    var ev = e.domEvent;
    var alt = ev.altKey;
    var shift = ev.shiftKey;
    var ctrl = ev.ctrlKey;
    var accel = e.getAccelKey();
    var button = e.getButton();
    
    if (ctrl && useragent.isMac)
        button = ev.button;

    if (e.editor.inMultiSelectMode && button == 2) {
        e.editor.textInput.onContextMenu(e.domEvent);
        return;
    }
    
    if (!ctrl && !alt && !accel) {
        if (button === 0 && e.editor.inMultiSelectMode)
            e.editor.exitMultiSelectMode();
        return;
    }
    
    if (button !== 0)
        return;

    var editor = e.editor;
    var selection = editor.selection;
    var isMultiSelect = editor.inMultiSelectMode;
    var pos = e.getDocumentPosition();
    var cursor = selection.getCursor();
    var inSelection = e.inSelection() || (selection.isEmpty() && isSamePoint(pos, cursor));

    var mouseX = e.x, mouseY = e.y;
    var onMouseSelection = function(e) {
        mouseX = e.clientX;
        mouseY = e.clientY;
    };
    
    var session = editor.session;
    var screenAnchor = editor.renderer.pixelToScreenCoordinates(mouseX, mouseY);
    var screenCursor = screenAnchor;
    
    var selectionMode;
    if (editor.$mouseHandler.$enableJumpToDef) {
        if (ctrl && alt || accel && alt)
            selectionMode = shift ? "block" : "add";
        else if (alt && editor.$blockSelectEnabled)
            selectionMode = "block";
    } else {
        if (accel && !alt) {
            selectionMode = "add";
            if (!isMultiSelect && shift)
                return;
        } else if (alt && editor.$blockSelectEnabled) {
            selectionMode = "block";
        }
    }
    
    if (selectionMode && useragent.isMac && ev.ctrlKey) {
        editor.$mouseHandler.cancelContextMenu();
    }

    if (selectionMode == "add") {
        if (!isMultiSelect && inSelection)
            return; // dragging

        if (!isMultiSelect) {
            var range = selection.toOrientedRange();
            editor.addSelectionMarker(range);
        }

        var oldRange = selection.rangeList.rangeAtPoint(pos);
        
        editor.inVirtualSelectionMode = true;
        
        if (shift) {
            oldRange = null;
            range = selection.ranges[0] || range;
            editor.removeSelectionMarker(range);
        }
        editor.once("mouseup", function() {
            var tmpSel = selection.toOrientedRange();

            if (oldRange && tmpSel.isEmpty() && isSamePoint(oldRange.cursor, tmpSel.cursor))
                selection.substractPoint(tmpSel.cursor);
            else {
                if (shift) {
                    selection.substractPoint(range.cursor);
                } else if (range) {
                    editor.removeSelectionMarker(range);
                    selection.addRange(range);
                }
                selection.addRange(tmpSel);
            }
            editor.inVirtualSelectionMode = false;
        });

    } else if (selectionMode == "block") {
        e.stop();
        editor.inVirtualSelectionMode = true;        
        var initialRange;
        var rectSel = [];
        var blockSelect = function() {
            var newCursor = editor.renderer.pixelToScreenCoordinates(mouseX, mouseY);
            var cursor = session.screenToDocumentPosition(newCursor.row, newCursor.column, newCursor.offsetX);

            if (isSamePoint(screenCursor, newCursor) && isSamePoint(cursor, selection.lead))
                return;
            screenCursor = newCursor;
            
            editor.selection.moveToPosition(cursor);
            editor.renderer.scrollCursorIntoView();

            editor.removeSelectionMarkers(rectSel);
            rectSel = selection.rectangularRangeBlock(screenCursor, screenAnchor);
            if (editor.$mouseHandler.$clickSelection && rectSel.length == 1 && rectSel[0].isEmpty())
                rectSel[0] = editor.$mouseHandler.$clickSelection.clone();
            rectSel.forEach(editor.addSelectionMarker, editor);
            editor.updateSelectionMarkers();
        };
        if (isMultiSelect && !accel) {
            selection.toSingleRange();
        } else if (!isMultiSelect && accel) {
            initialRange = selection.toOrientedRange();
            editor.addSelectionMarker(initialRange);
        }
        
        if (shift)
            screenAnchor = session.documentToScreenPosition(selection.lead);            
        else
            selection.moveToPosition(pos);
        
        screenCursor = {row: -1, column: -1};

        var onMouseSelectionEnd = function(e) {
            blockSelect();
            clearInterval(timerId);
            editor.removeSelectionMarkers(rectSel);
            if (!rectSel.length)
                rectSel = [selection.toOrientedRange()];
            if (initialRange) {
                editor.removeSelectionMarker(initialRange);
                selection.toSingleRange(initialRange);
            }
            for (var i = 0; i < rectSel.length; i++)
                selection.addRange(rectSel[i]);
            editor.inVirtualSelectionMode = false;
            editor.$mouseHandler.$clickSelection = null;
        };

        var onSelectionInterval = blockSelect;

        event.capture(editor.container, onMouseSelection, onMouseSelectionEnd);
        var timerId = setInterval(function() {onSelectionInterval();}, 20);

        return e.preventDefault();
    }
}