6.17.2   Editing Programs

The program window supports full text editing. Continuous portions of text can be selected by dragging with the mouse. An existing selection can be extended by holding down Shift and clicking the left mouse button. Double-clicking selects the word under the mouse pointer while triple-clicking selects the entire line.

To edit a program line in the operator window, double-click it with the left mouse button. If the operator window is not currently open, hold down Ctrl while double-clicking.

• The window title of the operator window clearly indicates that you are editing an existing program line. It also displays the procedure name and the line number.

• Clicking OK or Replace in the operator window will replace the original program line. This is even the case if the corresponding program line is no longer in view, for example, if a different procedure is selected in the program window.

  If the program line is deleted before the changes are committed in the operator window, the edited line will be inserted as a new program line at the IC. If you are in doubt about the current status, check the window title of the operator window.

Comments

Comments start with an asterisk (*) as the first character. You can also add comments at the end of regular program lines by introducing them with //.

  * this comment is ignored during program execution
  read_image (Image, 'clip')             // instantiate iconic variable
  threshold (Image, Region, 0, 63)       // select dark pixels

Special Input Formats

Certain operator calls can be entered in different formats. Syntactically, they are equivalent but the first variant is more readable and thus recommended. It is also the one used when entering the corresponding calls via the operator window.

• Variable assignments

  FileName := 'clip'
  assign('clip', FileName)                // deprecated
  

• Setting individual tuple elements

  Line[12] := 'text'
  assign_at(12, 'text', Line)             // deprecated
  

Note that for loops always have to be entered in the following format:

for Index := Start to End by Step
 ...
endfor

Line Continuation

Operator calls can span several lines for readability. A line can be continued by entering a backslash character as the last character of that line.

For example, you can enter

disp_arrow (WindowID, \
            Row[i], \
            Column[i], \
            Row[i]-Length*sin(Phi[i]), \
            Column[i]+Length*cos(Phi[i]), \
            4)

instead of

disp_arrow (WindowID, Row[i], Column[i], Row[i]-Length*sin(Phi[i]), Column[i]+...

Auto Indenting

The indent of new lines is adjusted automatically. Usually, the indent of the previous line is maintained. If a line is continued inside the parentheses of an operator call, the new line is indented up to the opening parenthesis. If the previous line opens a control structure (for example, if or while), the indent is increased by the indent size. The indent size is specified in the preferences (see Program Window). It defaults to four spaces. If a control structure is closed (for example, by entering endif or endwhile), the indent of the current line is decreased by the indent size.

Advanced Autocompletion

The program window provides advanced autocompletion to support you in several ways.

• Getting started

  HDevelop's autocompletion can assist you getting started with a completely empty program. Press Tab to get a list of typical first operators like dev_open_window and read_image.

  

• Suggestions for empty code lines

  Possible successors of the previous HALCON operator are suggested after pressing Tab.

  

  Press Shift+Tab to get suggestions for possible predecessors.

  

• Typing support

  When you start typing a new line, HDevelop will suggest a list of matching operator names:

  

  Note that the line is highlighted as invalid (red in the default color scheme) because it is still incomplete.

  The list is updated immediately as you continue typing:

  

  Press Tab to complete to the longest common string. In this example, only one operator name remains in the list. Thus, it is fully completed, including the opening parenthesis of the operator call:

  

  Once the cursor moves inside the parentheses, the suggestion list changes from operator mode, to parameter mode. The signature of the selected operator is displayed, and the parameter corresponding to the cursor position is highlighted in bold.

  The first entry in this list is a suggestion that completes the full operator call up to the closing parentheses. Again, typing ahead updates the list of suggestions accordingly. The remaining entries are suggestions for the first parameter of the operator call.

  Press Tab to select the first suggestion,

  

  or press Up or Down to step through the list entries,

  

  and press Tab or Return to select the highlighted entry. Then, enter a comma or press Tab again to get suggestions for the second parameter:

  

  Double-clicking the browse button in the suggestion list opens up a file selection dialog to specify the file name parameter. These browse buttons are included in the suggestions lists of all parameters that specify a file name.

  In this example, we want to load the image clip, so none of the suggestions fits. Just type the file name in single quotes ('clip') and press Tab to complete the parameter list. The closing parenthesis is inserted automatically:

  

  When entering expressions, the advanced autocompletion also suggests operations supported by the HDevelop language (see chapter “HDevelop Language”).

  

  Please note that the advanced autocompletion does not suggest legacy or deprecated operators. If you enter such an operator manually, a warning icon is displayed in the left column. Move the mouse cursor over this icon to get a tool tip with a corresponding warning message:

  

  The program window also supports autocompletion of block statements. When entering a control statement, for example, the control statement of a for loop, the corresponding end statement, for example, endfor of the block is automatically inserted by pressing Return.

Special Keyboard Shortcuts in the Program Window

Special Operator Handling

Some operators provide additional functionality when being edited. This functionality is available via an action button next to the parameter field in the operator window, or as an action button in the advanced autocompletion suggestion list.

If an operator contains a parameter that specifies a file name, the parameter value can be specified in a file selection dialog. See the previous section for an example (read_image).

The operators info_framegrabber and open_framegrabber provide a button to detect the available image acquisition interfaces automatically (see also 图像采集助手).