On Tue, Dec 18, 2018 at 9:31 AM Paul Dupuis via use-livecode < use-livecode@lists.runrev.com> wrote:
> > built under LiveCode 6.7.11. We are readying a new version built under > LC9.0.1, but without a recipe for the error, I have no way of testing > whether the new engine (and newer Datagrid) fixes this issue. I was > hoping the executionCotexts might provide some insight as to a suggested > recipe to reproduce the error. > I just checked the Data Grid script in 6.7.11 by executing the following code in the Message Box: ``` edit script of button id 1005 of stack "revDataGridLibrary" ``` If we piece together what we know from the error we get the following: 1) `_DrawListWithProperties` is called 2) `_table.DrawWithProperties` is called 3) `_table.DrawControlsInRealTime` is called 4) `_table.DrawColumns` is called 5) An object that doesn't exist is referenced and triggers the "can't find object". The line that triggers the "can't find object" error is line 3919. Line 3919 is part of the `_table.DrawColumns` private command which draws columns in a table. It reads as follows: ``` put the dgIndex of theControl into theCurrentIndex ``` This tells us that `theControl` doesn't exist. `theControl` comes from line 3910: ``` put line theControlIndex of theMasterControlList[theColumn] into theControl ``` `theMasterControlList` is a list of existing controls that can be used to render the data for a particular row and column in the table. What is interesting here is that `_DrawListWithProperties` is the entry point. `_DrawListWithProperties` is a private command and the error report isn't telling us who is calling `_DrawListWithProperties`. That complicates things a bit since we don't know if it is being called when you set the `dgData`, when the user is scrolling, when the user clicks on a row, etc. One potentially important piece of information is that `_DrawListWithProperties` can be called by `_ScrollListV`, Because scrolling can happen very quickly `_ScrollListV` will throttle itself meaning that if it is currently running when it is called (e.g. the user is scrolling quickly and `_ScrollListV` hasn't finished rendering the last scroll request) then it will call itself in time so that the new scroll request can be processed after the current scroll request finishes rendering. If `_DrawListWithProperties` was called from a scrolling action then the theory I propose below might be possible. Given what we know my best guess is that the columns property is being set and in the process a column is being removed. At the same time, `_DrawListWithProperties` is being triggered which is trying to draw the column that was removed. A `_ScrollListV` request sent in time might be able to create such a scenario. Now, all of this leads me to the following questions – 1) Are you modifying the columns displayed in this Data Grid through code? 2) If so, is it possible that you are updating the columns in the Data Grid while the user is interacting with it? -- Trevor DeVore CTO - ScreenSteps www.screensteps.com _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
