Difference between revisions of "IDE Window: Watch list"

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(Scope (Stackframe, Thread, History))
(Watch List: Update naming to match Lazarus 2.0.10; replace outdated image)
 
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{{IDE Window: Watch list}}
 
{{IDE Window: Watch list}}
[[category:IDE Window|Watch list]][[category:IDE Window - Debug|Watch list]][[category:Debugging]]
 
  
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== Navigation ==
  
= Important =  
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[[Main menu|Main Menu]] > [[Main menu#View|View]] > Debug Windows > Watches
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== Important ==  
  
 
You must [[Debugger_Setup |setup the debugger]] and start the project to debug it. Only then this window will be useful.
 
You must [[Debugger_Setup |setup the debugger]] and start the project to debug it. Only then this window will be useful.
 +
To open Watch list press Ctrl+Alt+W.
  
= Watch List =
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== Watches ==
  
[[File:Watch_List.png]]
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[[File:Watches_2_0_10.jpg|right]]
  
The "Watch List" shows the values of variables and expressions ("watches") when the debugged application is paused. (e.g. reached a breakpoint).
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The "Watches" window shows the values of variables and expressions when the debugged application is paused. (e.g. reached a breakpoint).
 
   
 
   
 
Expressions can be local or global variables, ([[GDB_Debugger_Tips#Properties|certain]]) properties, or pascal expressions (limited support, e.g. "a+1"). [[GDB_Debugger_Tips#Inspecting_Data-types_.28Watch.2FHint.29|See here for more information]]
 
Expressions can be local or global variables, ([[GDB_Debugger_Tips#Properties|certain]]) properties, or pascal expressions (limited support, e.g. "a+1"). [[GDB_Debugger_Tips#Inspecting_Data-types_.28Watch.2FHint.29|See here for more information]]
  
== Data displayed ==
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=== Data displayed ===
  
 
The display has 2 columns:
 
The display has 2 columns:
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*Expression: The variable or expression to be watched
 
*Expression: The variable or expression to be watched
 
*Value: The current value of the expression
 
*Value: The current value of the expression
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;Error...: The value could not be evaluated. (Error in Expression or Variable not available in selected scope.
 
;Error...: The value could not be evaluated. (Error in Expression or Variable not available in selected scope.
 
   
 
   
== Interface ==
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=== Interface ===
  
 
<u>Toolbar</u>
 
<u>Toolbar</u>
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;Copy Name: Copies the expression to the clipboard
 
;Copy Name: Copies the expression to the clipboard
 
;Copy Value: Copies the value to the clipboard
 
;Copy Value: Copies the value to the clipboard
<br style="clear:both" />
 
  
= Watch Properties =
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== Watch Properties ==
  
[[File:Watch_Properties.png]]
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[[File:Watch_Properties.png|right]]
  
;Expression: An Expression for which the evaluated value should be shown. Expressions can be local or global variables, ([[GDB_Debugger_Tips#Properties|certain]]) properties, or pascal expressions (limited support, e.g. "a+1").  
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;Expression: An expression for which the evaluated value should be shown. Expressions can be local or global variables, ([[GDB_Debugger_Tips#Properties|certain]]) properties, or pascal expressions (limited support, e.g. "a+1").  
;Repeat Count: Unimplemented
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;Repeat Count: Can be used to get array slices. The watch specifies the first element of the array "A[7]" (must have an index). With a "Repeat count" of 20, this shows A[7] to A[26]. It can also be used with a dynamic array (no index given). Then it specifies haw many elements to show, beginning with Item[0].
;Digits: Unimplemented
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;Digits: Not implemented.
;Enabled: See Enable/Disable above
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;Enabled: See Enable/Disable above.
;Allow function calls: Not yet supported
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;Allow function calls: Not yet supported.
 
;Use Instance class type: Objects are normally shown according to the declaration of the watched expression. Watching "Sender: TObject" will only show you data that is declared on TObject. However object variables can contain objects of inherited classes. Sender may be a TForm. Using this the debugger will find the actual class of the object and display all data.
 
;Use Instance class type: Objects are normally shown according to the declaration of the watched expression. Watching "Sender: TObject" will only show you data that is declared on TObject. However object variables can contain objects of inherited classes. Sender may be a TForm. Using this the debugger will find the actual class of the object and display all data.
 
;Style: How to display the data. If a style can not be applied, default will be used.
 
;Style: How to display the data. If a style can not be applied, default will be used.
  
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== See also ==
"Repeat Count"
 
:is implemented in Lazarus 1.1 (SVN, trunk). It can be used to get array slices. The watch specifies the first element of the array "A[7]" (must have an index). With a "Repeat count" of 20, this shows A[7] to A[26].
 
:It can also be used with a dynamic array (no index given). Then it specifies haw many elements to show, beginning with DynA[0]
 
 
 
= See Also =
 
  
TODO:
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* Watch-Points (Data-[[IDE_Window:Breakpoints|Breakpoints]])
* Watch-Points (Data-Breakpoints)
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* [[IDE_Window:_Evaluate/Modify|Evaluate Window]]
* Evaluate Window
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* [[IDE_Window:_Variable_Inspector|Debug Inspector]]
* Debug Inspector
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* [[IDE_Window:_Debug_History|Debug History]]
* Debug History
 

Latest revision as of 09:48, 1 February 2021

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Navigation

Main Menu > View > Debug Windows > Watches

Important

You must setup the debugger and start the project to debug it. Only then this window will be useful. To open Watch list press Ctrl+Alt+W.

Watches

Watches 2 0 10.jpg

The "Watches" window shows the values of variables and expressions when the debugged application is paused. (e.g. reached a breakpoint).

Expressions can be local or global variables, (certain) properties, or pascal expressions (limited support, e.g. "a+1"). See here for more information

Data displayed

The display has 2 columns:

  • Expression: The variable or expression to be watched
  • Value: The current value of the expression

Entries can be double-clicked to edit them.

Scope (Stackframe, Thread, History)

The values are evaluated according to the scope set in the Thread and Stack dialog. Default is the current Thread and top stack frame. Both (Stack and Frame) dialog offer to change the "current" Frame/Thread. The watch window will follow this selection.

It is also possible to select previously displayed values, using the History dialog.

Special Values

<invalid>
Value currently not available. Can be caused, if the debugger is not active or the debugged app not currently paused.
<evaluating>
Value is currently retrieved. A result will be show soon
<disabled>
The expression is excluded from evaluation. See Disable/Enable buttons (light bulbs)
Error...
The value could not be evaluated. (Error in Expression or Variable not available in selected scope.

Interface

Toolbar

debugger power.png Power
Enables/Disables all updates. This does not affect the enabled/disabled state of individual watches. This will freeze the current display.
laz add.png Add
Add a new expression. This will open the Watch property dialog. (It is also possible to double click an empty line in the list)
debugger enable.png Enable/debugger disable.png Disable
Enables/Disables individual watches from evaluation. This can be used to prevent spending time on evaluation, if a watch is not available in the current scope.
laz delete.png Remove
Deletes the selected Watch(es)
debugger enable all.png Enable all/debugger disable all.png Disable all
Enables/Disables all watches from evaluation.
menu clean.png Delete all
Cleans the list
menu environment options.png Properties
Change the expression or properties of the current/selected watch. (Also possible by double clicking the watch)

Context menu

Watch List popup.png

Additional to the above functionality the context menu allows to:

Inspect
Opens the current watch in the Debug-Inspector
Evaluate/Modify
Opens the current watch in the Evaluate/Modify window
Create Data/Watch Breakpoint
Opens the dialog to create a new watchpoint based on the current watch (stop if wachted value is changed or accessed)
Copy Name
Copies the expression to the clipboard
Copy Value
Copies the value to the clipboard

Watch Properties

Watch Properties.png
Expression
An expression for which the evaluated value should be shown. Expressions can be local or global variables, (certain) properties, or pascal expressions (limited support, e.g. "a+1").
Repeat Count
Can be used to get array slices. The watch specifies the first element of the array "A[7]" (must have an index). With a "Repeat count" of 20, this shows A[7] to A[26]. It can also be used with a dynamic array (no index given). Then it specifies haw many elements to show, beginning with Item[0].
Digits
Not implemented.
Enabled
See Enable/Disable above.
Allow function calls
Not yet supported.
Use Instance class type
Objects are normally shown according to the declaration of the watched expression. Watching "Sender: TObject" will only show you data that is declared on TObject. However object variables can contain objects of inherited classes. Sender may be a TForm. Using this the debugger will find the actual class of the object and display all data.
Style
How to display the data. If a style can not be applied, default will be used.

See also