Refactor setting filter and use safe strncpy

IncSet.c

@@ -29,6 +29,13 @@ void IncSet_reset(IncSet* this, IncType type) {
    IncMode_reset(&this->modes[type]);
 }
 
+void IncSet_setFilter(IncSet* this, const char* filter) {
+   IncMode* mode = &this->modes[INC_FILTER];
+   size_t len = String_safeStrncpy(mode->buffer, filter, sizeof(mode->buffer));
+   mode->index = len;
+   this->filtering = true;
+}
+
 static const char* const searchFunctions[] = {"Next  ", "Prev   ", "Cancel ", " Search: ", NULL};
 static const char* const searchKeys[] = {"F3", "S-F3", "Esc", "  "};
 static const int searchEvents[] = {KEY_F(3), KEY_F(15), 27, ERR};

IncSet.h

@@ -40,6 +40,8 @@ static inline const char* IncSet_filter(const IncSet* this) {
    return this->filtering ? this->modes[INC_FILTER].buffer : NULL;
 }
 
+void IncSet_setFilter(IncSet* this, const char* filter);
+
 typedef const char* (*IncMode_GetPanelValue)(Panel*, int);
 
 void IncSet_reset(IncSet* this, IncType type);

htop.c

@@ -248,13 +248,8 @@ static void setCommFilter(State* state, char** commFilter) {
    MainPanel* panel = (MainPanel*)state->panel;
    ProcessList* pl = state->pl;
    IncSet* inc = panel->inc;
-   size_t maxlen = sizeof(inc->modes[INC_FILTER].buffer) - 1;
-   char* buffer = inc->modes[INC_FILTER].buffer;
 
-   strncpy(buffer, *commFilter, maxlen);
-   buffer[maxlen] = 0;
-   inc->modes[INC_FILTER].index = strlen(buffer);
-   inc->filtering = true;
+   IncSet_setFilter(inc, *commFilter);
    pl->incFilter = IncSet_filter(inc);
 
    free(*commFilter);