winapi - tagRAWMOUSE Structure Issues -

i have set raw input trigger wm_input on message window. have set input mouse. succesfully getting messages , calling getrawinputdata().

i followed documentation letter being bit silly.

the docs struct receive:

rawmouse structure

so doing ctypes why im getting this.

when mouse wheel this:

tagrawmouse(0, 0, 1024, 0, 0, 0, 0) 

and when mouse wheel down exact same thing:

tagrawmouse(0, 0, 1024, 0, 0, 0, 0) 

as guide, when mouse move mouse gets this:

tagrawmouse(0, 0, 0, 0, 0, 1, 0) 

i set struct union 2 ushort ctypes not support union:

this.rawmouse = ctypes.structtype('tagrawmouse', [     { usflags: this.ushort },     { usbuttonflags: this.ushort },     { usbuttondata: this.ushort },     { ulrawbuttons: this.ulong },     { llastx: this.long },     { llasty: this.long },     { ulextrainformation: this.ulong } ]); 

does see wrong?

let's re-cap c++ definition of struct since important:

typedef struct tagrawmouse {   ushort usflags;   union {     ulong  ulbuttons;     struct {       ushort usbuttonflags;       ushort usbuttondata;     };   };   ulong  ulrawbuttons;   long   llastx;   long   llasty;   ulong  ulextrainformation; } rawmouse, *prawmouse, *lprawmouse; 

the union messing alignment. union needs aligned of members aligned. because union has ulong member, namely ulbuttons, union's alignment 4 bytes. therefore union has placed @ offset multiple of 4. in case places @ offset 4. , there 2 bytes of padding after usflags.

in ctypes struct, 2 ushort members of union overlay ulong, namely usbuttonflags , usbuttondata have alignment 2. therefore placed @ offsets 2 , 4. , padding has been lost in translation.

this sort of thing common, , 1 of first things check when translating struct. dig out c++ compiler , emit size of struct, , offsets members. compare same information translation. if don't match, work out why.

you have couple of ways fix it:

• replace usbuttonflags , usbuttondata ulong , use bitwise operations pick out 2 ushort values.
• add dummy padding ushort ahead of usbuttonflags.