Article:2767

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Applies To:

VB5

VB6

Author:

Steve McMahon

BugTrak

Bugs: 4 / 6

Issues: 6 / 6

Questions: 1 / 1

Updated:22 November 2003

11 May 2003

Calling remove on a non-existent tab did not raise an error because the control ate it.

Inserting a tab did not work correctly since the existing tabs were not shuffled up.

If a tab with a panel was removed, and then added, then a subscript out of range error occurred.

Thanks to Michael Elashoff, Julien Margail and Matt Funnell

Update History >

Subclassing Without The Crashes

Using the System Image List with (and without) vbAccelerator Controls

Flicker Free API Drawing

vbAccelerator ImageList Control and Class v2.0

vbAccelerator MDITabs Control

Null Pointer Crash with Blank Tab Caption

Summary

Id:	2767.1
Type:	Bug
Current Status:	Open

Detail

Project pTestTabs6, form frmTestTabs:

-------------------------------------Sub Form_Load()... Set c = .Tabs.Add("CONTENTS")...End Sub-------------------------------------

This Code results for the Project vbalDTab6, UserControl vbalDTabControl in

-------------------------------------Private Sub drawTabs(Optional ByVal lhDCTo As Long = 0)... If m_bIsNt Then DrawTextW lHDC, StrPtr(m_tTab(iC).sCaption), -1, tCalcR,DT_CALCRECT Or DT_LEFT Or DT_SINGLELINE Else DrawText lHDC, m_tTab(iC).sCaption, -1, tCalcR, DT_CALCRECTOr DT_LEFT Or DT_SINGLELINE End If...End Sub-------------------------------------

to StrPtr(m_tTab(iC).sCaption = 0 (means null, not a pointer to a nullstring!) Because of this the function DrawTextW() crashes the Application. So for a short workaround I changed the code as followed:

-------------------------------------Private Sub drawTabs(Optional ByVal lhDCTo As Long = 0)... If m_bIsNt Then Dim sp& sp = StrPtr(m_tTab(iC).sCaption) If sp Then DrawTextW lHDC, StrPtr(m_tTab(iC).sCaption), -1,tCalcR, DT_CALCRECT Or DT_LEFT Or DT_SINGLELINE Else DrawText lHDC, m_tTab(iC).sCaption, -1, tCalcR, DT_CALCRECT OrDT_LEFT Or DT_SINGLELINE End If...End Sub-------------------------------------

Maybe, in the case, it is especially required to set tCalcR to dedicated values, but it seems to work fine. The function DrawText() resp. DrawTextA() seems not to crash, but I couldn't test it under real conditions. Perhaps VB's UNICODE to ANSI conversion with ByVal corrects the problem.

For me this works fine.

Date of the tested software: 27/04/03

Environment: VS6.0 SP5, WinNT4.0/SP6a and WinXP/SP1a