c,user-interface,winapi , MessageBox won't work when handling WM_DESTROY event from DialogBox


MessageBox won't work when handling WM_DESTROY event from DialogBox

Question:

Tag: c,user-interface,winapi

While elaborating an answer for another question (by myself), I've come up with the idea of using a MessageBox to report the result of my dialog box. It is a WinAPI modal dialog box created with the DialogBox() function.

However, I noticed that handling WM_DESTROY in the dialog's procedure function will prevent the message box from appearing. I would like to understand the mechanics behind that.

Here's the full code, and the referred message box is at the end, right before return 0:

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <string.h>
#include "resource.h"

INT_PTR CALLBACK DlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_INITDIALOG:
        return (INT_PTR)TRUE;
    // uncomment these and the MessageBox won't show up
    //case WM_DESTROY:
        //PostQuitMessage(0);
        //break;
    case WM_COMMAND:
        switch (LOWORD(wParam))
        {
        case IDOK:
            if (MessageBoxW(hwnd, L"Close the window?", L"Confirm", MB_OKCANCEL) == IDOK)
                EndDialog(hwnd, (INT_PTR)wParam);
            break;
        case IDCANCEL:
            MessageBoxW(hwnd, L"Goodbye.", L"Close", MB_OK);
            EndDialog(hwnd, (INT_PTR)TRUE);
            break;
        }
    }
    return (INT_PTR)FALSE;
}

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow)
{
    INT_PTR ret = DialogBoxW(NULL, MAKEINTRESOURCEW(IDD_DIALOG1), NULL, DlgProc);

    wchar_t retTxt[10];
    if (ret == IDOK)
        wcscpy(retTxt, L"Alright!");
    else
        wcscpy(retTxt, L"Error");

    MessageBoxW(NULL, retTxt, L"Result", MB_OK);

    return 0;
}

Answer:

When you use DialogBox rather than DialogBoxParam, the dialog runs its own message loop that handles WM_DESTROY internally. When you post the WM_QUIT message from your dialog procedure you are generating an additional message* that the dialog box won't use, so it remains in your thread's message queue once the DialogBox function returns.

You then call MessageBox, which runs its own message loop. This immediately pulls the WM_QUIT out of the queue, exits the loop and returns before the dialog is even displayed.

(* actually it's not a "real" message - an internal flag is set that indicates quit has been posted - but the effect is the same on the subsequent message loop)


Related:


getchar() not working in c


c,while-loop,char,scanf,getchar
getchar() is not working in the below program, can anyone help me to solve this out. I tried scanf() function in place of getchar() then also it is not working. I am not able to figure out the root cause of the issue, can anyone please help me. #include<stdio.h> int...

How does ((a++,b)) work? [duplicate]


c,function,recursion,comma
This question already has an answer here: What does the comma operator `,` do in C? 8 answers In the below block of code, I am trying to understand how the line return reverse((i++, i)) is working. #include <stdio.h> void reverse(int i); int main() { reverse(1); } void reverse(int...

Efficient comparison of small integer vectors


c,integer,compare,bit-manipulation,string-comparison
I have small vectors. Each of them is made of 10 integers which are between 0 and 15. This means that every element in a vector can be written using 4 bits. Hence I can concatenate my vector elements and store the whole vector in a single long type (in...

What all local variables goto Data/BSS segment?


c++,c,nm
The man page of nm here: MAN NM says that The symbol type. At least the following types are used; others are, as well, depending on the object file format. If lowercase, the symbol is usually local; if uppercase, the symbol is global (external) And underneath it has "b" and...

execl() works on one of my code, but doesn't work on another


c,execl
I already used execl() in code, and it worked well. But this time, I really have no idea why it doesn't work. So here's the code that do not work #include <unistd.h> #include <stdio.h> int main() { int i = 896; printf("please\n"); execl("home/ubuntu/server/LC/admin/admin", (char*)i, NULL); printf("i have no idea why\n");...

Passing int using char pointer in C


c,exec,ipc
I'm trying to figure out how to pass an int using a char pointer. It fails once the int value is too large for the char. This is what I'm trying to figure out: char *args[5]; int i = 20; /*some other code/assignments*/ args[2] = (char *)&i; execv(path, args); How...

Python MVC style GUI Temperature Converter


python,user-interface,python-3.x,model-view-controller,tkinter
#The view (GuiTest.py) import tkinter import Controller class MyFrame(tkinter.Frame): def __init__(self, controller): tkinter.Frame.__init__(self) self.pack() self.controller = controller #Output Label self.outputLabel = tkinter.Label(self) self.outputLabel["text"] = ("") self.outputLabel.pack({"side":"right"}) #Entry Space self.entrySpace = tkinter.Entry(self) self.entrySpace["text"] = ("") self.entrySpace.pack({"side":"left"}) #two convert buttons self.convertButton=tkinter.Button(self) self.convertButton["text"]= "Fahrenheit to...

Loop through database table and compare user input


mysql,c
I am trying to loop through the rows in a MySql table and compare the data in a certain column to some user input using C. Currently my code looks like this: MYSQL *cxn = mysql_init(NULL); MYSQL_RES *result; unsigned int num_fields; unsigned int num_rows; char *query_string; MYSQL_ROW *row; if (mysql_real_connect(cxn,...

CGO converting Xlib XEvent struct to byte array?


c,go,xlib,cgo
I am creating a simple window manager (code based of the c code in tinywm) in Golang. To use Xlib, I am using cgo, so my header is: // #cgo LDFLAGS: -lX11 // #include <X11/Xlib.h> And I have a variable declaration, like: event := C.XEvent{} And then, I use this...

Does realloc() invalidate all pointers?


c,pointers,dynamic-memory-allocation,behavior,realloc
Note, this question is not asking if realloc() invalidates pointers within the original block, but if it invalidates all the other pointers. I'm new to C, and am a bit confused about the nature of realloc(), specifically if it moves any other memory. For example: void* ptr1 = malloc(2); void*...

C language, vector of struct, miss something?


c,vector,struct
This is a part of my program that I want to create a vector of struct typedef struct { char nome[501]; int qtd; int linha; int coluna; } tPeca; tPeca* criarPecas(FILE *pFile, int tam) { int i; tPeca *pecaJogo = (tPeca*)malloc(tam*sizeof(tPeca)); if (pecaJogo == NULL) return NULL; for (i =...

Array breaking in Pebble C


c,arrays,pebble-watch,cloudpebble
I'm trying to create a simple dice-rolling application in Pebble using C on CloudPebble. I have an array of different die sizes you can scroll through using Up/Down, and you roll (currently just generate a random number, it'll get fancier later) using the middle button. There's also a label at...

Java - Enforce TextField Format - UX - 00:00:00;00


java,regex,user-interface
Please see below image of the UI of my current application Currently, I am enforcing Data Format of the text fields in the back end. If the RegEx does match (00:00:00;00), it will throw an error. My question is from a UX perspective, is it possible to make the input...

scanf get multiple values at once


c,char,segmentation-fault,user-input,scanf
I need to get in one single shot different inputs from one single line. In particular I need to get a single char and then, depending on which char value I just read, it can be a string and an int or a string, an int and another string and...

Reverse ^ operator for decryption


c,algorithm,security,math,encryption
I'm trying to reverse the following code in order to provide a function which takes the buffer and decrypts it. void crypt_buffer(unsigned char *buffer, size_t size, char *key) { size_t i; int j; j = 0; for(i = 0; i < size; i++) { if(j >= KEY_SIZE) j = 0;...

Counting bytes received by posix read()


c,function,serial-port,posix
I get confused with one line of code: temp_uart_count = read(VCOM, temp_uart_data, 4096); I found more about read function at http://linux.die.net/man/3/read, but if everything is okay it returns 0, so how we can get num of bytes received from that? temp_uart_count is used to count how much bytes we received...

Disadvantages of calling realloc in a loop


c,memory-management,out-of-memory,realloc
I'm trying to implement some math algorithms in C on Windows 7, and I need to repeatedly increase size of my array. Sometimes it fails because realloc can't allocate memory. But if I allocate a lot of memory at once in the beginning it works fine. Is it a problem...

free causing different results from malloc


c,string,malloc,free
Below is a C program i have written to print different combination of characters in a string. This is not an efficient way as this algorithm creats a lot of extra strings. However my question is NOT about how to solve this problem more efficiently. The program works(inefficiently though) and...

close sub-window without closing main window PyGTK in python


python,user-interface,pygtk
I am creating a gui in python with PyGtk and I would like to create a sub-window that branches off from my main window but unlike a dialog the user will be able to interact with the main window without having to close the sub-window. The following code was demonstrated...

C binary tree sort - extending it


c,binary-tree,binary-search-tree
I need some help in C Help me to extend the binary tree sort on C. I need to return a sorted array in sort function. here it is: #include <stdio.h> #include <stdlib.h> struct btreenode { struct btreenode *leftchild ; int data ; struct btreenode *rightchild ; } ; void...

How to put an image on another image in python, using ImageTk?


python,user-interface,tkinter
I want to put an image in front of another one, then use this combined image as a button's background image in Tkinter. How can I do it? I am free to import Tkimage, Image. Clarify: I want to stick this on the center of this so that something like...

How does this code print odd and even?


c,if-statement,macros,logic
#define MACRO(num, str) {\ printf("%d", num);\ printf(" is");\ printf(" %s number", str);\ printf("\n");\ } int main(void) { int num; printf("Enter a number: "); scanf("%d", &num); if (num & 1) { MACRO(num, "Odd"); } else { MACRO(num, "Even"); } return 0; } Please explain the above code (if/else condition and how...

How to convert excel data to json at frontend side


excel,user-interface
I want to convert some excel data to JSON. Plan is to get my excel file from D drive, read data and make some UI for this. Can any one please help me out? Data is like this :- country year 1 2 3 4 Netherlands 1970 3603 4330 5080...

How to avoid user to click outside popup Dialog window using Qt and Python?


qt,user-interface,python-3.x,dialog,qt-creator
I created a Dialog window using Qt Creator and Python. I would like that Window stays on the top of my Gui AND avoid users to click outside that Dialog Until this dialog was closed.

Infinite loop with fread


c,arrays,loops,malloc,fread
I'm trying to allocate an array 64 bytes in size and then loop over the array indexes to put a read a byte each from the inputfile. but when I don't malloc() the array indexes, the loop stays in index0 (so each time it loops it replaces the content in...

Text justification C language


c,text,alignment
I have to solve a problem that involves left justification string length and leading zeros. I have the following table : BEGIN CLOSE CONCATENATE DELETE END INITIALIZE PRINT WRITE This is produced by a simple program. My problem is to find out how to convert it like that : It...

Is post-increment operator guaranteed to run instantly?


c,c89,post-increment,ansi-c
Let's say I have the following code: int i = 0; func(i++, i++); The increment is happening right after returning the value? Is it guaranteed that the first argument will be 0, and the second argument will be 1?...

How to read string until two consecutive spaces?


c,format,sscanf,c-strings
A well known function of the scanf() functions is that you can pass a format to scan input according to this format. For my case, I cannot seem to find a solution searching this and this documentation. I have a string (sInput) as the following: #something VAR1 this is a...

Is it safe to read and write on an array of 32 bit data byte by byte?


c,memory,memory-alignment
So I have a void * data of 32 bit unsigned integers which represents the pixels. Is it okay for me to access one of the pixels with a char * and modify the values directly? Or is it better to store my new pixel in a temporary uint32_t variable...

OpenGL glTexImage2D memory issue


c,opengl
I'm loading a cubemap to create a skybox, everything is fine and the skybox renders properly with a correct texture application. However, I decided to check my program safety with valgrind, Valgrind gives this error: http://pastebin.com/seqmXjyx The line 53 in sky.c is: glTexImage2D(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, 0, GL_RGB, texture.width, texture.height, 0,...

C programming - Confusion regarding curly braces


c,scope
The following code is for replacing multiple consecutive spaces into 1 space. Although I manage to do it, I am confused in the use of curly braces. This one is actually running fine: #include <stdio.h> #include <stdlib.h> int main() { int ch, lastch; lastch = 'a'; while((ch = getchar())!= EOF)...

C++ / C #define macro calculation


c++,c,macros
Suppose I have #define DETUNE1 sqrt(7)-sqrt(5) #define DETUNE2 sqrt(11)-sqrt(7) And I call these multiple times in my program. Are DETUNE1 and DETUNE2 calculated every time it is called? Thanks. Please don't downvote this, I really want to know and a search didn't turn up anything definite. ...

Program to reverse a string in C without declaring a char[]


c,string,pointers,char
I need to reverse a given string and display it without using the value At[index] notation , I tried the below program using pointers,but it does not print anything for the reverse string, Please help! int main() { char* name=malloc(256); printf("\nEnter string\n"); scanf("%s",name); printf("\nYou entered%s",name); int i,count; count=0; //find the...

Is there Predefined-Macros define about byte order in armcc


c,armcc,predefined-macro
Is there Predefined-Macros define about byte order in armcc. I am a novice on the armcc.and sorry for my English. In gcc these are macros: __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__ __ORDER_BIG_ENDIAN__ __ORDER_PDP_ENDIAN__ ... Now I have to use armcc, Is there same like these with armcc? Thank a lot. by the way,the armcc...

What does `strcpy(x+1, SEQX)` do?


c,strcpy
I'm wondering what this syntax of strcpy() does in line 65 and 66: 24 #define SEQX "TTCATA" 25 #define SEQY "TGCTCGTA" 61 M = strlen(SEQX); 62 N = strlen(SEQY); 63 x = malloc(sizeof(char) * (M+2)); /* +2: leading blank, and trailing \0 */ 64 y = malloc(sizeof(char) * (N+2)); 65...

Set precision dynamically using sprintf


c,printf,format-string
Using sprintf and the general syntax "%A.B" I can do this: double a = 0.0000005l; char myNumber[50]; sprintf(myNumber,"%.2lf",a); Can I set A and B dynamically in the format string?...

How to control C Macro Precedence


c,macros
#define VAL1CHK 20 #define NUM 1 #define JOIN(A,B,C) A##B##C int x = JOIN(VAL,NUM,CHK); With above code my expectation was int x = 20; But i get compilation error as macro expands to int x = VALNUMCHK; // Which is undefined How to make it so that NUM is replaced first...

How to change Eclipse IDE GUI icons?


eclipse,user-interface,icons
Elipse icons are ugly. Fact! I would like to replace the icons with more flat, monochromatic and minimalist icons, but I can't find documentation on how to change icons from Eclipse's user interface. How could I do this? It's needed to recompile eclipse?...

fread(), solaris to unix portability and use of uninitialised values


c,linux,memory,stack,portability
Valgrind found the following error and I, after reading the documentation, the code and other questions in here couldn't figure it out why. Valgrind: first warning ~$ valgrind --vgdb=yes --vgdb-error=0 --read-var-info=yes --leak-check=yes --track-origins=yes debitadmin* debitadmin ==20720== Conditional jump or move depends on uninitialised value(s) ==20720== at 0x4013BC6: initialise (dbg.c:199) ==20720==...

How convert unsigned int to unsigned char array


c++,c
I just need to extract those bytes using bitwise & operator. 0xFF is a hexadecimal mask to extract one byte. For 2 bytes, this code is working correctly: #include <stdio.h> int main() { unsigned int i = 0x7ee; unsigned char c[2]; c[0] = i & 0xFF; c[1] = (i>>8) &...

Segmentation Fault if I don't say int i=0


c,arrays,segmentation-fault,initialization,int
void removeVowels(char* array){ int i,j,v; i=0; char vowel[]={'a','e','i','o','u'}; while(array[i]!='\0') { for(v=0;v<5;v++) { if (array[i]==vowel[v]) { j=i; while(array[j]!='\0') { array[j]=array[j+1]; j++; } i--; break; } } i++; } } in function removeVowels() if I don't include i=0; and just say int i; why does it give segmentation fault? Isn't it automatically...

Does strlen() always correctly report the number of char's in a pointer initialized string?


c,strlen
As long as I use the char and not some wchar_t type to declare a string will strlen() correctly report the number of chars in the string or are there some very specific cases I need to be aware of? Here is an example: char *something = "Report all my...

CallXXXMethod undefined using JNI in C


java,c,jni
So I've tried to use the JNI interface to call Java methods from C. Calling static methods is no problem, but I get stuck when I want to call a method on an object. The code is as follows: #include <stdio.h> #include <string.h> #include <jni.h> int main() { JavaVMOption options[1];...

Segmentation fault with generating an RSA and saving in ASN.1/DER?


c,openssl,cryptography,rsa
#include <string.h> #include <openssl/aes.h> #include <openssl/rand.h> #include <openssl/bio.h> #include <openssl/rsa.h> #include <openssl/evp.h> #include <openssl/pem.h> #define RSA_LEN 2048 #define RSA_FACTOR 65537 int genRSA2048(unsigned char **pub,unsigned int *pub_l,unsigned char **priv,unsigned int *priv_l){ RSA *pRSA = NULL; pRSA = RSA_generate_key(RSA_LEN,RSA_FACTOR,NULL,NULL); if (pRSA){ pub_l = malloc(sizeof(pub_l)); *pub_l = i2d_RSAPublicKey(pRSA,pub); priv_l = malloc(sizeof(priv_l));...

Is i=i+1 an undefined behaviour?


c,increment,undefined-behavior
I'm using codeblocks and it is giving a different output to other compilers and I can't find a solution to it.What's the undefined behaviour in this program and is there any solution to avoid it? This is the code to print the nth number in a number system with only...

How to increment the value of an unsigned char * (C)


c++,c,openssl,byte,sha1
I have a value stored as an unsigned char * (in C). This holds the SHA1 hash of a string. My goal is to cover the SHA1 key space. Since I'm using <openssl/evp.h> to generate the hashes, I end up with an unsigned char* holding the SHA1 value. Now I...

Change background color of viewcontroller but not top area with clock


ios,user-interface,uiviewcontroller
I want to make my whole ViewController grey except I want the top area where it shows CARRIER and the current time to remain white. Is the only way just to stick a View that covers everything except that area, and set it to grey, or is there some way...

How can I align stack to the end of SRAM?


c,embedded,stm32,gnu-arm,coocox
I have a STM32F103VCT6 microcontroller with 48kb of SRAM, and recently i've got a memory collision: I have some static variable (lets call it A) located in heap with size of 0x7000 and I wrote some simple function to get info about stack and heap: void check(int depth) { char...

Galois LFSR - how to specify the output bit number


c,prng,shift-register
I am trying to understand how change the galois LFSR code to be able to specify the output bit number as a parameter for the function mentioned below. I mean I need to return not the last bit of LFSR as output bit, but any bit of the LFSR (...

VS2012 Identifer not found when part of static lib


c,visual-studio-2012,linker,static-libraries
Using VS2012 C/C++: I created and linked a static lib called "libtools" to my project. Calls to functions in the libtools lib worked as expected. I created and linked a second static lib called "shunt" to my project. But when I incorporate a call to a function in shunt, I...