How can I customize the completion of a GtkComboBoxText with both a "static" aspect and a "dynamic" one? The static aspect is because some entries are known and added to the combo-box-text at construction time with gtk_combo_box_text_append_text. The dynamic aspect is because I also need to complete thru some callback function(s), that is to complete dynamically -after creation of the GtkComboBoxText widget- once several characters has been typed.
My application uses Boehm's GC (except for GTK objects of course) like Guile or SCM or Bigloo are doing. It can be seen as an experimental persistent dynamic-typed programming language implementation with an integrated editor coded on and for Debian/Linux/x86-64 with the system GTK3.21 library, it is coded in C99 (some of which is generated) and is compiled with GCC6.
(I don't care about non-Linux systems, GTK3 libraries older than GTK3.20, GCC compiler older that GCC6)
question details
I'm entering (inputting into the GtkComboBoxText) either a name, or an object-id.
The name is C-identifier-like but starts with a letter and cannot end with an underscore. For example, comment, if, the_GUI, the_system, payload_json, or x1 are valid names (but _a0bcd or foobar_ are invalid names, because they start or end with an underscore). I currently have a big dozen of names, but I could have a few thousands of them. So it would be reasonable to offer a completion once only a single or perhaps two letters has been typed, and completion for names can happen statically because they are not many of them (so I feel reasonable to call gtk_combo_box_append_text for each name).
The object-id starts with an underscore followed by a digit and has exactly 18 alphanumeric (sort-of random) characters. For example, _5Hf0fFKvRVa71ZPM0, _8261sbF1f9ohzu2Iu, _0BV96V94PJIn9si1K are possible object-ids. Actually it is 96 almost random bits (probably only 294 are possible). The object-id plays the role of UUIDs (in the sense that it is assumed to be world-wide unique for distinct objects) but has a C friendly syntax. I currently have a few dozen of objects-ids, but I could have a few hundred of thousands (or maybe a million) of them. But given a prefix of four characters like _6S3 or _22z, I am assuming that only a reasonable number (probably at most a dozen, and surely no more than a thousand) object-ids exist in my application with that prefix. Of course it would be unreasonable to register (statically) a priori all the object ids (the completion has to happen after four characters have been typed, and should happen dynamically).
So I want a completion that works both on names (e.g. typing one letter perhaps followed by another alphanum character should be enough to propose a completion of at most a hundred choices), and on object-ids (typing four characters like _826 should be enough to trigger a completion of probably at most a few dozen choices, perhaps a thousand ones if unlucky).
Hence typing the three keys p a tab would offer completion with a few names like payload_json or payload_vectval etc... and typing the five keys _ 5 H f tab would offer completion with very few object-ids, notably _5Hf0fFKvRVa71ZPM0
sample incomplete code
So far I coded the following:
static GtkWidget *
mom_objectentry (void)
{
GtkWidget *obent = gtk_combo_box_text_new_with_entry ();
gtk_widget_set_size_request (obent, 30, 10);
mo_value_t namsetv = mo_named_objects_set ();
I have Boehm-garbage-collected values, and mo_value_t is a pointer to any of them. Values can be tagged integers, pointers to strings, objects, or tuples or sets of objects. So namesetv now contains the set of named objects (probably less than a few thousand of named objects).
int nbnam = mo_set_size (namsetv);
MOM_ASSERTPRINTF (nbnam > 0, "bad nbnam");
mo_value_t *namarr = mom_gc_alloc (nbnam * sizeof (mo_value_t));
int cntnam = 0;
for (int ix = 0; ix < nbnam; ix++)
{
mo_objref_t curobr = mo_set_nth (namsetv, ix);
mo_value_t curnamv = mo_objref_namev (curobr);
if (mo_dyncast_string (curnamv))
namarr[cntnam++] = curnamv;
}
qsort (namarr, cntnam, sizeof (mo_value_t), mom_obname_cmp);
for (int ix = 0; ix < cntnam; ix++)
gtk_combo_box_text_append_text (GTK_COMBO_BOX_TEXT (obent),
mo_string_cstr (namarr[ix]));
at this point I have sorted all the (few thousands at most) names and added "statically" them using gtk_combo_box_text_append_text.
GtkWidget *combtextent = gtk_bin_get_child (GTK_BIN (obent));
MOM_ASSERTPRINTF (GTK_IS_ENTRY (combtextent), "bad combtextent");
MOM_ASSERTPRINTF (gtk_entry_get_completion (GTK_ENTRY (combtextent)) ==
NULL, "got completion in combtextent");
I noticed with a bit of surprise that gtk_entry_get_completion (GTK_ENTRY (combtextent)) is null.
But I am stuck here. I am thinking of:
Having some mom_set_complete_objectid(const char*prefix) which given a prefix like "_47n" of at least four characters would return a garbage collected mo_value_t representing the set of objects with that prefix. This is very easy to code for me, and is nearly done.
Make my own local GtkEntryCompletion* mycompl = ..., which would complete like I want. Then I would put it in the text entry combtextent of my gtk-combo-box-text using gtk_entry_set_completion(GTK_ENTRY(combtextent), mycompl);
Should it use the entries added with gtk_combo_box_text_append_text for the "static" name completion role? How should I dynamically complete using the dynamic set value returned from my mom_set_complete_objectid; given some object-pointer obr and some char bufid[20]; I am easily and quickly able to fill it with the object-id of that object obr with mo_cstring_from_hi_lo_ids(bufid, obr->mo_ob_hid, obr->mo_ob_loid)..
I don't know how to code the above. For reference, I am now just returning the combo-box-text:
// if the entered text starts with a letter, I want it to be
// completed with the appended text above if the entered text starts
// with an undersore, then a digit, then two alphanum (like _0BV or
// _6S3 for example), I want to call a completion function.
#warning objectentry: what should I code here?
return obent;
} /* end mom_objectentry */
Is my approach the right one?
The mom_objectentry function above is used to fill modal dialogs with short lifetime.
I am favoring simple code over efficiency. Actually, my code is temporary (I'm hoping to bootstrap my language, and generate all its C code!) and in practice I'll probably have only a few hundred names and at most a few dozen of thousands of object-ids. So performance is not very important, but simplicity of coding (some conceptually "throw away" code) is more important.
I don't want (if possible) to add my own GTK classes. I prefer using existing GTK classes and widgets, customizing them with GTK signals and callbacks.
context
My application is an experimental persistent programming language and implementation with a near Scheme or Python (or JavaScript, ignoring the prototype aspect, ...) semantics but with a widely different (not yet implemented in september 7th, 2016) syntax (to be shown & input in GTK widgets), using the Boehm garbage collector for values (including objects, sets, tuples, strings...)... Values (including objects) are generally persistent (except the GTK related data : the application starts with a nearly empty window). The entire language heap is persisted in JSON-like syntax in some Sqlite "database" (generated at application exit) dumped into _momstate.sql which is re-loaded at application startup. Object-ids are useful to show object references to the user in GTK widgets, for persistence, and to generate C code related to the objects (e.g. the object of id _76f7e2VcL8IJC1hq6 could be related to a mo_76f7e2VcL8IJC1hq6 identifier in some generated C code; this is partly why I have my object-id format instead of using UUIDs).
PS. My C code is GPLv3 free software and available on github. It is the MELT monitor, branch expjs, commit e2b3b99ef66394...
NB: The objects mentioned here are implicitly my language objects, not GTK objects. The all have a unique object-id, and some but not most of them are named.
I will not show exact code on how to do it because I never did GTK & C only GTK & Python, but it should be fine as the functions in C and Python functions can easily be translated.
OP's approach is actually the right one, so I will try to fill in the gaps. As the amount of static options is limited probably won't change to much it indeed makes sense to add them using gtk_combo_box_text_append which will add them to the internal model of the GtkComboBoxText.
Thats covers the static part, for the dynamic part it would be perfect if we could just store this static model and replace it with a temporay model using gtk_combo_box_set_model() when a _ was found at the start of the string. But we shouldn't do this as the documentation says:
You should not call gtk_combo_box_set_model() or attempt to pack more cells into this combo box via its GtkCellLayout interface.
So we need to work around this, one way of doing this is by adding a GtkEntryCompletion to the entry of the GtkComboBoxText. This will make the entry attempt to complete the current string based on its current model. As an added bonus it can also add all the character all options have in common like this:
As we don't want to load all the dynamic options before hand I think the best approach will be to connect a changed listener to the GtkEntry, this way we can load the dynamic options when we have a underscore and some characters.
As the GtkEntryCompletion uses a GtkListStore internally, we can reuse part of the code Nominal Animal provided in his answer. The main difference being: the connect is done on the GtkEntry and the replacing of GtkComboText with GtkEntryCompletion inside the populator. Then everything should be fine, I wish I would be able to write decent C then I would have provided you with code but this will have to do.
Edit: A small demo in Python with GTK3
import gi
gi.require_version('Gtk', '3.0')
import gi.repository.Gtk as Gtk
class CompletingComboBoxText(Gtk.ComboBoxText):
def __init__(self, static_options, populator, **kwargs):
# Set up the ComboBox with the Entry
Gtk.ComboBoxText.__init__(self, has_entry=True, **kwargs)
# Store the populator reference in the object
self.populator = populator
# Create the completion
completion = Gtk.EntryCompletion(inline_completion=True)
# Specify that we want to use the first col of the model for completion
completion.set_text_column(0)
completion.set_minimum_key_length(2)
# Set the completion model to the combobox model such that we can also autocomplete these options
self.static_options_model = self.get_model()
completion.set_model(self.static_options_model)
# The child of the combobox is the entry if 'has_entry' was set to True
entry = self.get_child()
entry.set_completion(completion)
# Set the active option of the combobox to 0 (which is an empty field)
self.set_active(0)
# Fill the model with the static options (could also be used for a history or something)
for option in static_options:
self.append_text(option)
# Connect a listener to adjust the model when the user types something
entry.connect("changed", self.update_completion, True)
def update_completion(self, entry, editable):
# Get the current content of the entry
text = entry.get_text()
# Get the completion which needs to be updated
completion = entry.get_completion()
if text.startswith("_") and len(text) >= completion.get_minimum_key_length():
# Fetch the options from the populator for a given text
completion_options = self.populator(text)
# Create a temporary model for the completion and fill it
dynamic_model = Gtk.ListStore.new([str])
for completion_option in completion_options:
dynamic_model.append([completion_option])
completion.set_model(dynamic_model)
else:
# Restore the default static options
completion.set_model(self.static_options_model)
def demo():
# Create the window
window = Gtk.Window()
# Add some static options
fake_static_options = [
"comment",
"if",
"the_GUI",
"the_system",
"payload_json",
"x1",
"payload_json",
"payload_vectval"
]
# Add the the Combobox
ccb = CompletingComboBoxText(fake_static_options, dynamic_option_populator)
window.add(ccb)
# Show it
window.show_all()
Gtk.main()
def dynamic_option_populator(text):
# Some fake returns for the populator
fake_dynamic_options = [
"_5Hf0fFKvRVa71ZPM0",
"_8261sbF1f9ohzu2Iu",
"_0BV96V94PJIn9si1K",
"_0BV1sbF1f9ohzu2Iu",
"_0BV0fFKvRVa71ZPM0",
"_0Hf0fF4PJIn9si1Ks",
"_6KvRVa71JIn9si1Kw",
"_5HKvRVa71Va71ZPM0",
"_8261sbF1KvRVa71ZP",
"_0BKvRVa71JIn9si1K",
"_0BV1KvRVa71ZPu2Iu",
"_0BV0fKvRVa71ZZPM0",
"_0Hf0fF4PJIbF1f9oh",
"_61sbFV0fFKn9si1Kw",
"_5Hf0fFKvRVa71ozu2",
]
# Only return those that start with the text
return [fake_dynamic_option for fake_dynamic_option in fake_dynamic_options if fake_dynamic_option.startswith(text)]
if __name__ == '__main__':
demo()
Gtk.main()
Here is my suggestion:
Use a GtkListStore to contain a list of GTK-managed strings (essentially, copies of your identifier string) that match the current prefix string.
(As documented for gtk_list_store_set(), a G_TYPE_STRING item is copied. I consider the overhead of the extra copy acceptable here; it should not affect real-world performance much anyway, I think, and in return, GTK+ will manage the reference counting for us.)
The above is implemented in a GTK+ callback function, which gets an extra pointer as payload (set at the time the GUI is created or activated; I suggest you use some structure to keep references you need to generate the matches). The callback is connected to the combobox popup signal, so that it gets called whenever the list is expanded.
Note that as B8vrede noted in a comment, a GtkComboBoxText should not be modified via its model; that is why one should/must use a GtkComboBox instead.
Practical example
For simplicity, let's assume all the data you need to find or generate all known identifiers matched against is held in a structure, say
struct generator {
/* Whatever data you need to generate prefix matches */
};
and the combo box populator helper function is then something like
static void combo_box_populator(GtkComboBox *combobox, gpointer genptr)
{
struct generator *const generator = genptr;
GtkListStore *combo_list = GTK_LIST_STORE(gtk_combo_box_get_model(combobox));
GtkWidget *entry = gtk_bin_get_child(GTK_BIN(combobox));
const char *prefix = gtk_entry_get_text(GTK_ENTRY(entry));
const size_t prefix_len = (prefix) ? strlen(prefix) : 0;
GtkTreeIter iterator;
/* Clear the current store */
gtk_list_store_clear(combo_list);
/* Initialize the list iterator */
gtk_tree_model_get_iter_first(GTK_TREE_MODEL(combo_list), &iterator);
/* Find all you want to have in the combo box;
for each const char *match, do:
*/
gtk_list_store_append(combo_list, &iterator);
gtk_list_store_set(combo_list, &iterator, 0, match, -1);
/* Note that the string pointed to by match is copied;
match is not referred to after the _set() returns.
*/
}
When the UI is built or activated, you need to ensure the GtkComboBox has an entry (so the user can write text into it), and a GtkListStore model:
struct generator *generator;
GtkWidget *combobox;
GtkListStore *combo_list;
combo_list = gtk_list_store_new(1, G_TYPE_STRING);
combobox = gtk_combo_box_new_with_model_and_entry(GTK_TREE_MODEL(combo_list));
gtk_combo_box_set_id_column(GTK_COMBO_BOX(combobox), 0);
gtk_combo_box_set_entry_text_column(GTK_COMBO_BOX(combobox), 0);
gtk_combo_box_set_button_sensitivity(GTK_COMBO_BOX(combobox), GTK_SENSITIVITY_ON);
g_signal_connect(combobox, "popup", G_CALLBACK(combo_box_populator), generator);
On my system, the default pop-up accelerator is Alt+Down, but I assume you've already changed that to Tab.
I have a crude working example here (a .tar.xz tarball, CC0): it reads lines from standard input, and lists the ones matching the user prefix in reverse order in the combo box list (when popped-up). If the entry is empty, the combobox will contain all input lines. I didn't change the default accelerators, so instead of Tab, try Alt+Down.
I also have the same example, but using GtkComboBoxText instead, here (also CC0). This does not use a GtkListStore model, but uses gtk_combo_box_text_remove_all() and gtk_combo_box_text_append_text() functions to manipulate the list contents directly. (There is just a few different lines in the two examples.) Unfortunately, the documentation is not explicit whether this interface references or copies the strings. Although copying is the only option that makes sense, and this can be verified from the current Gtk+ sources, the lack of explicit documentation makes me hesitant.
Comparing the two examples I linked to above (both grab some 500 random words from /usr/share/dict/words if you compile and run it with make), I don't see any speed difference. Both use the same naïve way of picking prefix matches from a linked list, which means the two methods (GtkComboBox + model, or GtkComboBoxText) should be about equally fast.
On my own machine, both get annoyingly slow with more than 1000 or so matches in the popup; with just a hundred or less matches, it feels instantaneous. This, to me, indicates that the slow/naïve way of picking prefix matches from a linked list is not the culprit (because the entire list is traversed in both cases), but that the GTK+ combo boxes are just not designed for large lists. (The slowdown is definitely much, much worse than linear.)
Related
can someone tell me what is the difference between coping one transaction(item) to the another like in examples bellow (add_method_port_1 and add_method_port_2):
add_method_port_1 (added_item: item_s) is {
var new_item: new_item_s;
gen new_item keeping {
it.my_trans_s == added_item.as_a(t_trans_s);
};
};
add_method_port_2 (added_item: item_s) is {
var new_item : new_item_s = deep_copy(added_item.as_a(t_trans_s));
};
Where new_item_s looks like:
struct new_item_s like item_s {
%my_trans_s: t_trans_s;
};
Thanks,
Andrija
Actually, the results of the two methods are different even if the assumption mentioned in Rodion's answer does hold.
With the first method, new_item points to the same my_trans_s object as the original added_item, because the constraint it.my_trans_s == added_item.as_a(t_trans_s) means pointer equality.
With the second method, new_item points to a copy of the original my_trans_s, because deep_copy copies everything recursively.
In this specific example, assuming that new_item_s has only one field my_trans_s, there is no difference in outcome.
In practice, the meaning and the goal of "gen keeping" and deep_copy is quite different:
gen keeping, even with '==' constraints, practically assignments, means random-constraint generating an item executing iGen logic engine; if this is a struct then pre_generate and post_generate methods are invoked, and all the fields not mentioned in 'keeping {}' block are also randomly generated according to existing constraints and their type properties. It is usually used to create a new item for which only some properties are known.
deep_copy creates an exact copy (up to some minor nuances) of the given struct, and if it has fields which are also structs - copy of all connected graph topology. There is no random generation, no special methods, no logical engine executed. Usually it used to capture the data at some point for later analysis.
In other words, if the assumption "new_item_s has only one field my_trans_s" is wrong, the result are going to be very much different.
I am used to being able to perform a binary search of a sorted list of, say, Strings or Integers, with code along the lines of:
Vector<String> vstr = new Vector<String>();
// etc...
int index = Collections.binarySearch (vstr, "abcd");
I'm not clear on how codenameone handles standard java methods and classes, but it looks like this could be fixed easily if classes like Integer and String (or the codenameone versions of these) implemented the Comparable interface.
Edit: I now see that code along the lines of the following will do the job.
int index = Collections.binarySearch(vstr, "abcd", new Comparator<String>() {
#Override
public int compare(String object1, String object2) {
return object1.compareTo(object2);
}
});
Adding the Comparable interface (to the various primitive "wrappers") would also would also make it easier to use Collections.sort (another very useful method :-))
You can also sort with a comparator but I agree, this is one of the important enhancements we need to provide in the native VM's on the various platforms personally this is my biggest peeve in our current VM.
Can you file an RFE on that and mention it as a comment in the Number issue?
If we are doing that change might as well do both.
Its quite a big task but ill try to explain.
I have an array with a list of 200 strings and I want to be able to randomly select one and add it to the stage using code. I have movieclips exported for actionscript with the same class name as the strings in the array. Also, if it is possible, would I be able to select the strings with predictability such as the first has a 0.7 chance the second a 0.1 etc. Here is what i have currently
var nameList:Array=["Jimmy","Bob","Fred"]
var instance:DisplayObject = createRandom(nameList);
addChild(instance);
function createRandom(typeArray:Array):*
{
// Select random String from typeArray.
var selection:String = typeArray[ int(Math.random() * typeArray.length) ];
// Create instance of relevant class.
var Type:Class = getDefinitionByName(selection) as Class;
// Return created instance.
return new Type();
}
All this throws me this error
ReferenceError: Error #1065: Variable [class Jimmy] is not defined.
Ive searched for other threads similar but none combine the three specific tasks of randomisation, predictability and addChild().
I think that you've got two problems: a language problem and a logic problem. In the .fla connected to your code above, in the Library find each symbol representing a name and write into the 'AS linkage' column for that symbol the associated name -- e.g., 'Bob,' 'Fred' -- just the name, no punctuation.
Now getDefinitionByName() will find your 'Class'
If you put a different graphic into each MovieClip -- say, a piece of fruit or a picture of Bob,Jim, Fred -- and run your program you'll get a random something on stage each time.
That should solve your language problem. But the logic problem is a little harder, no?
That's why I pointed you to Mr. Kelly's solution (the first one, which for me is easier to grasp).
I spent quite a lot of time in looking for the full documentation of all the C API XLM Functions without success.
I found this page which illustrate a few of them:
http://msdn.microsoft.com/en-us/library/office/bb687910%28v=office.12%29.aspx
But for instance I wanted to understand and use xlfAddMenu, and I cannot find a page on MSDN that explain me.
Do you know if there is any documentation available? Apparently it is not so easy to get there.
There is no exhaustive official documentation for all C API XLM functions. However, as the documentation says following regarding C API XLM functions:
Many more functions are exposed by Excel via the C API that are useful
when you are developing XLLs. They correspond to the Excel worksheet
functions and functions and commands that are available from XLM macro
sheets."
Also, the EXAMPLE.[C,H] files which comme with the installation of the SDK use some of these functions and you can use it to learn how to use them. For instance, the xlfAddMenu is used in the xlAutoOpen callback function.
// In the following block of code, the Generic drop-down menu is created.
// Before creation, a check is made to determine if Generic already
// exists. If not, it is added. If the menu needs to be added, memory is
// allocated to hold the array of menu items. The g_rgMenu[] table is then
// transferred into the newly created array. The array is passed as an
// argument to xlfAddMenu to actually add the drop-down menu before the
// help menu. As a last step the memory allocated for the array is
// released.
//
// This block uses TempStr12() and TempNum12(). Both create a temporary
// XLOPER12. The XLOPER12 created by TempStr12() contains the string passed to
// it. The XLOPER12 created by TempNum12() contains the number passed to it.
// The Excel12f() function frees the allocated temporary memory. Both
// functions are part of the framework library.
Excel12f(xlfGetBar, &xTest, 3, TempInt12(10), TempStr12(L"Generic"), TempInt12(0));
if (xTest.xltype == xltypeErr)
{
hMenu = GlobalAlloc(GMEM_MOVEABLE,sizeof(XLOPER12) * g_rgMenuCols * g_rgMenuRows);
px = pxMenu = (LPXLOPER12) GlobalLock(hMenu);
for (i=0; i < g_rgMenuRows; i++)
{
for (j=0; j < g_rgMenuCols; j++)
{
px->xltype = xltypeStr;
px->val.str = TempStr12(g_rgMenu[i][j])->val.str;
px++;
}
}
xMenu.xltype = xltypeMulti;
xMenu.val.array.lparray = pxMenu;
xMenu.val.array.rows = g_rgMenuRows;
xMenu.val.array.columns = g_rgMenuCols;
Excel12f(xlfAddMenu,0,3,TempNum12(10),(LPXLOPER12)&xMenu,TempStr12(L"Help"));
GlobalUnlock(hMenu);
GlobalFree(hMenu);
}
According to me the best documentation (but not updated..) is the following book : Financial Applications using Excel Add-in Development in C / C++, 2nd Edition by Steve Dalton. You can find description of the xlfAddMenu function page 332. You can also find some useful information in the chm file of the Microsoft Excel XLL Software Development Kit, including codes examples (note I did not found the xlfAddMenu in it so I guess it is a depreciated function).
INT GetTree (HWND hWnd, HTREEITEM hItem, HKEY *pRoot, TCHAR *pszKey,
INT nMax) {
TV_ITEM tvi;
TCHAR szName[256];
HTREEITEM hParent;
HWND hwndTV = GetDlgItem (hWnd, ID_TREEV);
memset (&tvi, 0, sizeof (tvi));
hParent = TreeView_GetParent (hwndTV, hItem);
if (hParent) {
// Get the parent of the parent of the...
GetTree (hWnd, hParent, pRoot, pszKey, nMax);
// Get the name of the item.
tvi.mask = TVIF_TEXT;
tvi.hItem = hItem;
tvi.pszText = szName;
tvi.cchTextMax = dim(szName);
TreeView_GetItem (hwndTV, &tvi); //send the TVM_GETITEM message?
lstrcat (pszKey, TEXT ("\\"));
lstrcat (pszKey, szName);
} else {
*pszKey = TEXT ('\0');
szName[0] = TEXT ('\0');
// Get the name of the item.
tvi.mask = TVIF_TEXT | TVIF_PARAM;
tvi.hItem = hItem;
tvi.pszText = szName;
tvi.cchTextMax = dim(szName);
if (TreeView_GetItem (hwndTV, &tvi))
//*pRoot = (HTREEITEM)tvi.lParam; //original
hItem = (HTREEITEM)tvi.lParam;
else {
INT rc = GetLastError();
}
}
return 0;
}
The block of code that begins with the comment "Get the name of the item" does not make sense to me. If you are getting the listview item why does the code set the parameters of the item being retrieved? If you already had the values there would be no need to retrieve them.
Secondly near the comment "original" is the original line of code which will compile with a warning under embedded visual c++ 4.0, but if you copy the exact same code into visual studio 2008 it will not compile. Since I did not write any of this code, and am trying to learn, is it possible the original author made a mistake on this line? The *pRoot should point to HKEY type yet he is casting to an HTREEITEM type which should never work since the data types don't match?
The block of code that begins with the comment "Get the name of the item" does not make sense to me. If you are getting the listview item why does the code set the parameters of the item being retrieved, because if you already had the values there would be no need to retrieve them.
After that comment, the first line is to specify to TreeView_GetItem (which, by the way, is actually a SendMessage in disguise) that we want to retrieve the text of the item and the associated lParam. The next line specifies the handle to the item about which we want information.
The following line specifies where the retrieved text must be saved, i.e. in the szName buffer, which has been allocated at the beginning of the function; the last line before the function call specifies the size of such buffer, so to avoid buffer overflows.
I suggest you to have a look at the documentation of TreeView_GetItem and of TVITEM to understand better what's going on.
Secondly near the comment "original" is the original line of code which will compile with a varning under embedded visual c++, but if you copy the exact same code into visual studio 2008 it will not compile. Since I did not write any of this code and am trying to learn is it possible the original author made a mistake on this line, since the *pRoot should point to and HKEY type yet he is casting to an HTREEITEM type which should never work since the data types don't match?
It's not clear what the code is trying to do there; at first glance I'd say that in the lParam associated to each item in the root node of the treeview is stored a handle to a registry key, and the procedure retrieves it in that way. Still, if it was like that, the (HTREEITEM) cast wouldn't make sense at all; probably it was a mistake, forgiven by the compiler because it treated all handles as plain void *; if my hypothesis is correct you should keep the original line, just replacing (HTREEITEM) with (HKEY).
Many times, API calls take in information in a structure, and also return information in the same structure. If you look at the documentation for TreeView_GetItem, it will clearly show how it operates.
As for the second question, are you compiling as C++? What is the error?
The LPTVITEM parameter to the TreeView_GetItem macro is used bi-directionally.
TreeView_GetItem does indeed send the TVM_GETITEM message to the treeview. What's going on here is that the caller fills in a little bit of the struct to say "here's what I have and what I want" and then the treeview will fill in the requested bits.
From the TreeView_GetItem documentation
When the TVM_GETITEM message is sent, the hItem member of the TVITEM or TVITEMEX structure identifies the item to retrieve information about, and the mask member specifies the attributes to retrieve.
For the second part, I think it looks like it was a mistake, based on the names of the variables etc., but you should probably check how the function is used in the rest of the code to make sure.
The first question is pretty simple: you're filling in a few of the items in the structure to tell what data you want, then calling TreeView_GetItem to actually retrieve the specified data. In this case, you're specifying TVIF_TEXT, which says you want the text for the particular item. You also give it a buffer where it's going to put the text (szName), and tell it how long that buffer is (so it won't write past the end of the buffer). When you call TreeView_GetIem, it copies the text for that item into your buffer.
As to your second question: it looks like all that code (both old and new) is somewhat problematic. The general intent seems to be to retrieve the path to the item that was originally passed in, but it seems to do that rather poorly. It starts by recursively walking up the tree to the root. Then it retrieves the text for the root item, but only into the local variable szName -- which it then ignores (does not copy into szKey). It does store the handle to the root item into hItem (this is where it originally wrote to pRoot).
Then, as it returns (walking back "down" the tree), it retrieves the text for each item, and appends those names to szKey (separated by '\'), to form (most of) the path to the item originally passed in. Unfortunately, as it does this, it ignores the nMax that was passed in, so it can (apparently) write past the end of the szKey buffer.