File "connection_checker.js"
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/**
* @license
* Copyright 2020 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @fileoverview An object that encapsulates logic for checking whether a potential
* connection is safe and valid.
* @author [email protected] (Rachel Fenichel)
*/
'use strict';
goog.provide('Blockly.ConnectionChecker');
goog.require('Blockly.constants');
goog.require('Blockly.registry');
goog.requireType('Blockly.Connection');
goog.requireType('Blockly.IConnectionChecker');
/**
* Class for connection type checking logic.
* @implements {Blockly.IConnectionChecker}
* @constructor
*/
Blockly.ConnectionChecker = function() {
};
/**
* Check whether the current connection can connect with the target
* connection.
* @param {Blockly.Connection} a Connection to check compatibility with.
* @param {Blockly.Connection} b Connection to check compatibility with.
* @param {boolean} isDragging True if the connection is being made by dragging
* a block.
* @param {number=} opt_distance The max allowable distance between the
* connections for drag checks.
* @return {boolean} Whether the connection is legal.
* @public
*/
Blockly.ConnectionChecker.prototype.canConnect = function(a, b,
isDragging, opt_distance) {
return this.canConnectWithReason(a, b, isDragging, opt_distance) ==
Blockly.Connection.CAN_CONNECT;
};
/**
* Checks whether the current connection can connect with the target
* connection, and return an error code if there are problems.
* @param {Blockly.Connection} a Connection to check compatibility with.
* @param {Blockly.Connection} b Connection to check compatibility with.
* @param {boolean} isDragging True if the connection is being made by dragging
* a block.
* @param {number=} opt_distance The max allowable distance between the
* connections for drag checks.
* @return {number} Blockly.Connection.CAN_CONNECT if the connection is legal,
* an error code otherwise.
* @public
*/
Blockly.ConnectionChecker.prototype.canConnectWithReason = function(
a, b, isDragging, opt_distance) {
var safety = this.doSafetyChecks(a, b);
if (safety != Blockly.Connection.CAN_CONNECT) {
return safety;
}
// If the safety checks passed, both connections are non-null.
var connOne = /** @type {!Blockly.Connection} **/ (a);
var connTwo = /** @type {!Blockly.Connection} **/ (b);
if (!this.doTypeChecks(connOne, connTwo)) {
return Blockly.Connection.REASON_CHECKS_FAILED;
}
if (isDragging &&
!this.doDragChecks(
/** @type {!Blockly.RenderedConnection} **/ (a),
/** @type {!Blockly.RenderedConnection} **/ (b),
opt_distance || 0)) {
return Blockly.Connection.REASON_DRAG_CHECKS_FAILED;
}
return Blockly.Connection.CAN_CONNECT;
};
/**
* Helper method that translates a connection error code into a string.
* @param {number} errorCode The error code.
* @param {Blockly.Connection} a One of the two connections being checked.
* @param {Blockly.Connection} b The second of the two connections being
* checked.
* @return {string} A developer-readable error string.
* @public
*/
Blockly.ConnectionChecker.prototype.getErrorMessage = function(errorCode,
a, b) {
switch (errorCode) {
case Blockly.Connection.REASON_SELF_CONNECTION:
return 'Attempted to connect a block to itself.';
case Blockly.Connection.REASON_DIFFERENT_WORKSPACES:
// Usually this means one block has been deleted.
return 'Blocks not on same workspace.';
case Blockly.Connection.REASON_WRONG_TYPE:
return 'Attempt to connect incompatible types.';
case Blockly.Connection.REASON_TARGET_NULL:
return 'Target connection is null.';
case Blockly.Connection.REASON_CHECKS_FAILED:
var connOne = /** @type {!Blockly.Connection} **/ (a);
var connTwo = /** @type {!Blockly.Connection} **/ (b);
var msg = 'Connection checks failed. ';
msg += connOne + ' expected ' + connOne.getCheck() + ', found ' + connTwo.getCheck();
return msg;
case Blockly.Connection.REASON_SHADOW_PARENT:
return 'Connecting non-shadow to shadow block.';
case Blockly.Connection.REASON_DRAG_CHECKS_FAILED:
return 'Drag checks failed.';
default:
return 'Unknown connection failure: this should never happen!';
}
};
/**
* Check that connecting the given connections is safe, meaning that it would
* not break any of Blockly's basic assumptions (e.g. no self connections).
* @param {Blockly.Connection} a The first of the connections to check.
* @param {Blockly.Connection} b The second of the connections to check.
* @return {number} An enum with the reason this connection is safe or unsafe.
* @public
*/
Blockly.ConnectionChecker.prototype.doSafetyChecks = function(a, b) {
if (!a || !b) {
return Blockly.Connection.REASON_TARGET_NULL;
}
if (a.isSuperior()) {
var blockA = a.getSourceBlock();
var blockB = b.getSourceBlock();
} else {
var blockB = a.getSourceBlock();
var blockA = b.getSourceBlock();
}
if (blockA == blockB) {
return Blockly.Connection.REASON_SELF_CONNECTION;
} else if (b.type != Blockly.OPPOSITE_TYPE[a.type]) {
return Blockly.Connection.REASON_WRONG_TYPE;
} else if (blockA.workspace !== blockB.workspace) {
return Blockly.Connection.REASON_DIFFERENT_WORKSPACES;
} else if (blockA.isShadow() && !blockB.isShadow()) {
return Blockly.Connection.REASON_SHADOW_PARENT;
}
return Blockly.Connection.CAN_CONNECT;
};
/**
* Check whether this connection is compatible with another connection with
* respect to the value type system. E.g. square_root("Hello") is not
* compatible.
* @param {!Blockly.Connection} a Connection to compare.
* @param {!Blockly.Connection} b Connection to compare against.
* @return {boolean} True if the connections share a type.
* @public
*/
Blockly.ConnectionChecker.prototype.doTypeChecks = function(a, b) {
var checkArrayOne = a.getCheck();
var checkArrayTwo = b.getCheck();
if (!checkArrayOne || !checkArrayTwo) {
// One or both sides are promiscuous enough that anything will fit.
return true;
}
// Find any intersection in the check lists.
for (var i = 0; i < checkArrayOne.length; i++) {
if (checkArrayTwo.indexOf(checkArrayOne[i]) != -1) {
return true;
}
}
// No intersection.
return false;
};
/**
* Check whether this connection can be made by dragging.
* @param {!Blockly.RenderedConnection} a Connection to compare.
* @param {!Blockly.RenderedConnection} b Connection to compare against.
* @param {number} distance The maximum allowable distance between connections.
* @return {boolean} True if the connection is allowed during a drag.
* @public
*/
Blockly.ConnectionChecker.prototype.doDragChecks = function(a, b, distance) {
if (a.distanceFrom(b) > distance) {
return false;
}
// Don't consider insertion markers.
if (b.getSourceBlock().isInsertionMarker()) {
return false;
}
switch (b.type) {
case Blockly.PREVIOUS_STATEMENT:
return this.canConnectToPrevious_(a, b);
case Blockly.OUTPUT_VALUE: {
// Don't offer to connect an already connected left (male) value plug to
// an available right (female) value plug.
if ((b.isConnected() &&
!b.targetBlock().isInsertionMarker()) ||
a.isConnected()) {
return false;
}
break;
}
case Blockly.INPUT_VALUE: {
// Offering to connect the left (male) of a value block to an already
// connected value pair is ok, we'll splice it in.
// However, don't offer to splice into an immovable block.
if (b.isConnected() &&
!b.targetBlock().isMovable() &&
!b.targetBlock().isShadow()) {
return false;
}
break;
}
case Blockly.NEXT_STATEMENT: {
// Don't let a block with no next connection bump other blocks out of the
// stack. But covering up a shadow block or stack of shadow blocks is
// fine. Similarly, replacing a terminal statement with another terminal
// statement is allowed.
if (b.isConnected() &&
!a.getSourceBlock().nextConnection &&
!b.targetBlock().isShadow() &&
b.targetBlock().nextConnection) {
return false;
}
break;
}
default:
// Unexpected connection type.
return false;
}
// Don't let blocks try to connect to themselves or ones they nest.
if (Blockly.draggingConnections.indexOf(b) != -1) {
return false;
}
return true;
};
/**
* Helper function for drag checking.
* @param {!Blockly.Connection} a The connection to check, which must be a
* statement input or next connection.
* @param {!Blockly.Connection} b A nearby connection to check, which
* must be a previous connection.
* @return {boolean} True if the connection is allowed, false otherwise.
* @protected
*/
Blockly.ConnectionChecker.prototype.canConnectToPrevious_ = function(a, b) {
if (a.targetConnection) {
// This connection is already occupied.
// A next connection will never disconnect itself mid-drag.
return false;
}
// Don't let blocks try to connect to themselves or ones they nest.
if (Blockly.draggingConnections.indexOf(b) != -1) {
return false;
}
if (!b.targetConnection) {
return true;
}
var targetBlock = b.targetBlock();
// If it is connected to a real block, game over.
if (!targetBlock.isInsertionMarker()) {
return false;
}
// If it's connected to an insertion marker but that insertion marker
// is the first block in a stack, it's still fine. If that insertion
// marker is in the middle of a stack, it won't work.
return !targetBlock.getPreviousBlock();
};
Blockly.registry.register(Blockly.registry.Type.CONNECTION_CHECKER,
Blockly.registry.DEFAULT, Blockly.ConnectionChecker);