Fixed #99 forgot to set clipboard callbacks

Previously if you use `nk_edit_string` and use flag
`NK_EDIT_CLIPBOARD`, callbacks were not passed. I only tested it with
`nk_edit_buffer` and set the callbacks directly. This wrong behavior
is now fixed and should work copy & paste should behave correctly.

demo/allegro5/main.c

@@ -93,7 +93,7 @@ main(void)
             if (nk_option_label(ctx, "easy", op == EASY)) op = EASY;
             if (nk_option_label(ctx, "hard", op == HARD)) op = HARD;
 
-            nk_layout_row_dynamic(ctx, 22, 1);
+            nk_layout_row_dynamic(ctx, 25, 1);
             nk_property_int(ctx, "Compression:", 0, &property, 100, 10, 1);
 
             {struct nk_panel combo;

demo/glfw/main.c

@@ -100,7 +100,7 @@ int main(void)
             if (nk_option_label(ctx, "easy", op == EASY)) op = EASY;
             if (nk_option_label(ctx, "hard", op == HARD)) op = HARD;
 
-            nk_layout_row_dynamic(ctx, 22, 1);
+            nk_layout_row_dynamic(ctx, 25, 1);
             nk_property_int(ctx, "Compression:", 0, &property, 100, 10, 1);
 
             {struct nk_panel combo;

demo/sdl/main.c

@@ -69,13 +69,13 @@ main(void)
     {struct nk_font_atlas *atlas;
     nk_sdl_font_stash_begin(&atlas);
     /*struct nk_font *droid = nk_font_atlas_add_from_file(atlas, "../../../extra_font/DroidSans.ttf", 14, 0);*/
-    /*struct nk_font *robot = nk_font_atlas_add_from_file(atlas, "../../../extra_font/Robot-Regular.ttf", 14, 0);*/
+    /*struct nk_font *roboto = nk_font_atlas_add_from_file(atlas, "../../../extra_font/Roboto-Regular.ttf", 16, 0);*/
     /*struct nk_font *future = nk_font_atlas_add_from_file(atlas, "../../../extra_font/kenvector_future_thin.ttf", 13, 0);*/
     /*struct nk_font *clean = nk_font_atlas_add_from_file(atlas, "../../../extra_font/ProggyClean.ttf", 12, 0);*/
     /*struct nk_font *tiny = nk_font_atlas_add_from_file(atlas, "../../../extra_font/ProggyTiny.ttf", 10, 0);*/
     /*struct nk_font *cousine = nk_font_atlas_add_from_file(atlas, "../../../extra_font/Cousine-Regular.ttf", 13, 0);*/
     nk_sdl_font_stash_end();
-    /*nk_style_set_font(ctx, &droid->handle)*/;}
+    /*nk_style_set_font(ctx, &roboto->handle)*/;}
 
     background = nk_rgb(28,48,62);
     while (running)
@@ -98,13 +98,14 @@ main(void)
             enum {EASY, HARD};
             static int op = EASY;
             static int property = 20;
+
             nk_layout_row_static(ctx, 30, 80, 1);
             if (nk_button_label(ctx, "button", NK_BUTTON_DEFAULT))
                 fprintf(stdout, "button pressed\n");
             nk_layout_row_dynamic(ctx, 30, 2);
             if (nk_option_label(ctx, "easy", op == EASY)) op = EASY;
             if (nk_option_label(ctx, "hard", op == HARD)) op = HARD;
-            nk_layout_row_dynamic(ctx, 22, 1);
+            nk_layout_row_dynamic(ctx, 25, 1);
             nk_property_int(ctx, "Compression:", 0, &property, 100, 10, 1);
 
             {struct nk_panel combo;

demo/x11/main.c

@@ -138,7 +138,7 @@ main(void)
             nk_layout_row_dynamic(ctx, 30, 2);
             if (nk_option_label(ctx, "easy", op == EASY)) op = EASY;
             if (nk_option_label(ctx, "hard", op == HARD)) op = HARD;
-            nk_layout_row_dynamic(ctx, 22, 1);
+            nk_layout_row_dynamic(ctx, 25, 1);
             nk_property_int(ctx, "Compression:", 0, &property, 100, 10, 1);
         }
         nk_end(ctx);}

nuklear.h

@@ -12764,18 +12764,19 @@ nk_do_edit(nk_flags *state, struct nk_command_buffer *out,
         /* cut & copy handler */
         {int copy= nk_input_is_key_pressed(in, NK_KEY_COPY);
         int cut = nk_input_is_key_pressed(in, NK_KEY_CUT);
-        if ((copy || cut) && (flags & NK_EDIT_CLIPBOARD) && edit->clip.copy)
+        if ((copy || cut) && (flags & NK_EDIT_CLIPBOARD))
         {
             int glyph_len;
             nk_rune unicode;
             const char *text;
-            int begin = edit->select_start;
-            int end = edit->select_end;
+            int b = edit->select_start;
+            int e = edit->select_end;
 
-            begin = NK_MIN(begin, end);
-            end = NK_MAX(begin, end);
+            int begin = NK_MIN(b, e);
+            int end = NK_MAX(b, e);
             text = nk_str_at_const(&edit->string, begin, &unicode, &glyph_len);
-            edit->clip.copy(edit->clip.userdata, text, end - begin);
+            if (edit->clip.copy)
+                edit->clip.copy(edit->clip.userdata, text, end - begin);
             if (cut){
                 nk_textedit_cut(edit);
                 cursor_follow = nk_true;
@@ -17541,6 +17542,8 @@ nk_edit_buffer(struct nk_context *ctx, nk_flags flags,
             edit->select_start = edit->cursor;
             edit->select_end = edit->cursor;
         }
+        if (flags & NK_EDIT_CLIPBOARD)
+            edit->clip = ctx->clip;
     }
 
     filter = (!filter) ? nk_filter_default: filter;