Public domain by Jamal Mazrui
Layout by Code (LbC) is an approach to designing graphical user interfaces via specialized routines rather than graphical layout tools. Those tools tend to be visually and mouse oriented, and thus challenging for blind programmers to use reliably and efficiently. The first implementation of LbC is in the free programming language called AutoIt, available from
The file LbC.au3, included in this distribution archive, is a function library that may be included in an AutoIt program. It requires the latest beta version of the interpreter, available from
All LbC functions start with the _lbc prefix. The underline character is conventional for user defined functions in AutoIt. For convenient typing, the letters of this prefix are in lower case. For readability, the next part of the function name begins with a capital letter. For example, the _lbcTest function displays a message box for checking the value of a variable or expression.
LbC global variables and constants begin with a lower case letter indicating the data type, followed by the Lbc prefix. In this case, no underscore is used, and the L is capitalized for readability. The rest of the identifier name also begins with a capital letter. For example, $nLbcHLabelPad is a constant that stores the amount of pixels that horizontally separates a label from its associated control.
LbC currently supports eight types of AutoIt controls: label, button, check box, radio button, list box, input, edit, and status bar. These controls are created with a function like _lbcCtrlCreateInput. Following AutoIt naming conventions, the word Control is abbreviated CTRL. The control creation functions take eight optional parameters corresponding to the caption, data, left, top, width, height, style, and extended style attributes of the control. Often, one need only specify the caption. Sometimes, the caption and data are specified. If particular values are needed for parameters, the intervening parameters can either be explicitly specified or given a value of -1, indicating that the LbC default should be used. The TestLbC.au3 program illustrates the use of these and other LbC functions.
The concepts of group and band are useful for describing a form. A group is a set of related controls with arrow navigation support among them. Generally, a set of radio buttons will constitute a group. Related check boxes could also constitute a group. Another group might include An edit box and related button for picking rather than typing a value.
A band is a horizontal series of controls within a group. A group contains at least one band, and may contain a vertical series of bands, that is, multiple bands arranged consecutively below each other. Each band may be identified by a unique number that corresponds to its sequential value during the creation process of the form. The first band is numbered 1, the second band 2, and so on. Groups are numbered similarly. For example, group 3 is the third group created, which might contain bands 5 and 6.
By default, each control in a band has the same coordinate value for its top border--the vertical position in the form. The bottom border may vary depending on whether the control is a single or multi line control, e.g., a list box or multi line edit box. The height of a band is the height of its tallest control.
LbC spaces controls according to the "Official Guidelines for User Interface Design," a Microsoft publication based on years of usability research and experience. Much of the information is from the web page
Spacing between controls varies depending on whether they are related, and if so, whether the relationship is between a label and its associated control. Controls that do not have their own captions have labels instead. A label is positioned to the left of its associated control. It has the "Static" window class and a colon at the end of its text.
The Microsoft publication mentioned above gives layout guidelines in terms of "dialog units." By definition, a horizontal dialog unit is one quarter of the average character width of the default system font. A vertical unit is one eigth of the average character height. Thus, an average character is four dialog units wide and eight dialog units high. At the time of this writing, most personal computers seem to use a default system font of either "MS Sansarif" or "Tahoma" and a screen resolution where each dialog unit is two pixels in size. Thus, each character is eight pixels wide and 16 pixels high on average.
According to the guidelines, three dialog units separate a label and associated control. Four dialog units separate other related controls in the same group. Seven dialog units separate unrelated controls in consecutive groups.
This LbC spacing applies both horizontally and vertically. For example, the top of a new band of controls will be placed four dialog units down if part of the same group, or seven dialog units down if part of a new group. Note that a band to the right of another band is necessarily part of a different group--because a band is a set of related controls. Thus, two bands arranged horizontally are separated by the group divider spacing of seven dialog units. Since the AutoIt language actually uses pixel coordinates rather than dialog units, LbC converts accordingly.
LbC uses the concept of a layout cursor that points to where the next control created will be placed on the form. The column and row position of this cursor is stored in global variables that LbC adjusts automatically behind the scenes. All LbC global variables, by the way, start with a lower case letter for the data type, followed by Lbc and then the rest of the variable name, e.g., $nLbcRow and $nLbcCol store numeric values for the column and row of the layout cursor.
Three functions start a new band of controls: _lbcStartBand, _lbcStartVGroup, and _lbcStartHGroup. They take an optional parameter indicating the reference band for alignment. For example, _lbcStartBand(3) starts a new band of controls below the third one. The layout cursor is positioned at the column corresponding to the left border of band 3. Its row is lower than the bottom border of band 3 by the amount of vertical spacing for related controls. When a control is created in the new band, the layout cursor is moved beyond the right border of the control by a standard spacing amount (three dialog units if the control is a label, or four otherwise).
The function _lbcStartVGroup starts a new group in the vertical direction, whereas _lbcStartHGroup startes one in the horizontal direction. Calling _lbcStartVGroup(3) positions the layout cursor at the same column as _lbcStartBand(3), but at a row further down, since group divider spacing is used (seven dialog units). Calling _lbcStartHGroup(3) instead would position the layout cursor so that its row corresponds to the top border of band 3, and its column is beyond the right border of band 3 by the amount for group divider spacing. When a reference band is not specified as a parameter to these band or group initiation functions, LbC defaults to the current band.
A set of similarly named functions uses the word Get instead of Set, and compares multiple controls if an ID list is used rather than a single ID. For example, _lbcCtrlGetLeft returns the lowest left value of the controls passed in the ID parameter. _lbcCtrlGetWidth returns the total width between the control border that is furthest to the left and the one that is furthest to the right.
Several functions return an ID or ID list to be used as a parameter in subsequent function calls. The functions _lbcCtrlGetLeftMost /TopMost /RightMost /BottomMost /Tallest /Widest return the ID of the control with the extreme value of the specified attribute. The functions _lbcBandGetIdList and _lbcGroupGetIdList return the IDs in the group or band specified by number. If no value or a value of -1 is given, then the current group or band nunber is used. _lbcWinGetIdList returns all IDs in the form.
The functions _lbcCtrlGetIdBySeq /Class /Text return an ID based on the sequence number of the control, its class sequence, or textual data. For example, _lbcCtrlGetIdBySeq(1) returns the ID of the first control in the form; _lbcCtrlGetIdByClass(Edit2") returns the ID of the second edit box; and _lbcCtrlGetIdByText("Last name:") returns the ID of the control with that text, which is probably a control of the Static class serving as a label.
Some functions change the position of controls within a band. _lbcBandHCenter horizontally centers the controls so that the left and right margins are equal. _lbcBandEvenSpace divides the space so that the same amount is between controls and also in the margins. _lbcBandRespace applies the default LbC spacing rules, separating each control by the label padding, related control padding, or divider group padding as appropriate. These functions may also take a list of band numbers separated by the vertical bar (|) character, applying the spacing operation to each band. _lbcWinRespace respaces every band of the form. This may be needed if, say, the height of a control is changed, thus affecting appropriate placement of the next band of controls.
The function _lbcCtrlSetState sets the state of one or more controls, e.g., to a hidden or disabled state. The functions _lbcCtrlAddStyle /ExStyle and _lbcCtrlDelStyle /ExStyle add or delete a style or extended style.
LbC may operate on windows created with programming languages other than AutoIt. One would still write AutoIt code, but the LbC functions could interrogate or manipulate controls on a form of another application. Only a subset of LbC functions would be applicable, e.g., not those that depend on bands or groups, since these are LbC data structures filled by the LbC commands to create controls, bands, or groups.
To reference an external form with LbC, use the LbCSwitch function, passing it the window handle of interest (which may be found with native AutoIt functions such as WinGetHandle). Now, LbC functions that use an ID or ID list as a parameter will do so in the context of the external form. For example, the _lbcWinGenCode function may be used to generate AutoIt code that creates a form similar to the referenced one.
An alphabetized summary of nearly 100 LbC functions is below. Besides the sample code in the TestLbC.au3 file, a good way of learning this library is by searching for a function of interest in the LbC.au3 file, since larger functions often use smaller ones as building blocks.
I welcome feedback and suggestions for improving Layout by Code. I will try to assist anyone in using the AutoIt implementation, or in porting it to another programming language.
February 22, 2006
_lbcBandEvenHeight = Set height of controls to tallest in band
_lbcBandEvenSpace = Set same spacing between controls and in margins of band
_lbcBandGetGroup = Get group of band
_lbcBandGetIdList = Get Ids in band
_lbcBandHCenter = Horizontally center band, making left and right margins equal
_lbcBandLJustify = Left justify controls in band
_lbcBandReSpace = Set default LbC spacing for controls in band
_lbcBandRJustify = Right justify controls in band
_lbcBandSetHeight = Set height of controls in band
_lbcChoose = Prompt user to choose from set of buttons
_lbcClassGetIdList = Get Ids of class
_lbcCreate = Create parent form for child controls
_lbcCtrlAddExStyle = Ad extended style to control
_lbcCtrlAddId = Add Ids from second ID list to first one
_lbcCtrlAddStyle = Add style to control
_lbcCtrlCreateButton = Create push button
_lbcCtrlCreateCheckBox = Create check box
_lbcCtrlCreateEdit = Create multi-line edit box
_lbcCtrlCreateInput = Create single-line input box
_lbcCtrlCreateLabel = Create label
_lbcCtrlCreateList = Create list box
_lbcCtrlCreateRadio = Create radio button
_lbcCtrlCreateStatusBar = Create status bar
_lbcCtrlDelExStyle = Delete extended style of control
_lbcCtrlDelId = Delete IDs in second ID list from first one
_lbcCtrlDelStyle = Delete style of control
_lbcCtrlGetBand = Get band of control
_lbcCtrlGetBorders = Get array of left, top, right, and bottom borders of control
_lbcCtrlGetBottom = Get bottom border of control
_lbcCtrlGetBottommost = Get ID of bottom-most control
_lbcCtrlGetClass = Get class of control
_lbcCtrlGetExStyle = Get extended style of control
_lbcCtrlGetFontName = Get font name of text in control
_lbcCtrlGetGroup = Get group of control
_lbcCtrlGetHCenter = Get horizontal center of control, mid-point between left and right borders
_lbcCtrlGetHeight = Get height of control
_lbcCtrlGetIdByClass = Get ID by class of control
_lbcCtrlGetIdByHandle = Get ID by handle of control
_lbcCtrlGetIdBySeq = Get ID by sequence of control in form
_lbcCtrlGetIdByText = Get ID by text of control
_lbcCtrlGetLeft = Get left border of control
_lbcCtrlGetLeftmost = Get ID of left-most control
_lbcCtrlGetMargins = Get array of left, top, right, and bottom margins of control
_lbcCtrlGetNarrowest = Get ID of narrowest control
_lbcCtrlGetRight = Get right border of control
_lbcCtrlGetRightmost = Get ID of right-most control
_lbcCtrlGetShortest = Get ID of shortest control
_lbcCtrlGetStyle = Get style of control
_lbcCtrlGetTallest = Get ID of tallest control
_lbcCtrlGetText = Get Text of control
_lbcCtrlGetTextHeight = Get height of text in control
_lbcCtrlGetTextWidest = Get text width of control with widest text
_lbcCtrlGetTextWidth = Get width of text in control
_lbcCtrlGetTop = Get top border of control
_lbcCtrlGetTopmost = Get ID of top-most control
_lbcCtrlGetVCenter = Get vertical center of control, mid-point between top and bottom borders
_lbcCtrlGetWidest = Get ID of widest control
_lbcCtrlGetWidth = Get width of control
_lbcCtrlSetBottom = Set bottom border of control
_lbcCtrlSetData = Set text or other data of control
_lbcCtrlSetHCenter = Set horizontal center of control, mid-point between left and right borders
_lbcCtrlSetHeight = Set height of control
_lbcCtrlSetLeft = Set left border of control
_lbcCtrlSetRight = Set right border of control
_lbcCtrlSetState = Set state of control
_lbcCtrlSetTop = Set top of control
_lbcCtrlSetVCenter = Set vertical center of control, mid-point between top and bottom borders
_lbcCtrlSetWidth = Set width of control
_lbcDelete = Delete form
_lbcDesktopGetClientHeight = Get height of Windows desktop, not including taskbar
_lbcGroupGetBandList = Get bands of group
_lbcGroupGetIdList = Get IDs of group
_lbcHelp = Present user with read-only, multi-line edit box of information
_lbcPick = Prompt user to pick item from list
_lbcSay = Speak a string via the API of JAWS or Window-Eyes
_lbcSetCol = Set column of layout cursor
_lbcSetRow = Set row of layout cursor
_lbcShow = Show form
_lbcStartBand = Start new band of controls
_lbcStartHGroup = Start new horizontal group of controls
_lbcStartVGroup = Start new vertical group of controls
_lbcStatusBarGetHandle = Get handle of status bar
_lbcStatusBarGetText = Get text of status bar
_lbcStatusBarResize = Resize status bar
_lbcStatusBarSetText = Set text of status bar
_lbcSwitch = Switch reference to another form
_lbcTest = Display simple message box
_lbcTestCoord = Display message box with coordinates of control
_lbcU2X = Convert horizontal dialog units to pixels
_lbcU2Y = Convert vertical dialog units to pixels
_lbcWinGenCode = Generate native AutoIt code to produce a form designed with LbC
_lbcWinGetBandList = Get bands of form
_lbcWinGetClassList = Get classes of form
_lbcWinGetExStyle = Get extended style of form
_lbcWinGetHandle = Get handle of form
_lbcWinGetIdList = Get IDs of form
_lbcWinGetStyle = Get style of form
_lbcWinReSpace = Set default LbC spacing for form