Development | Starting Out

Saddling the HTML View Control Part II / Catch Those Messages
Written by Alex Yakhnin  [author's bio]  [read 39132 times]
Edited by Derek

         

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Introduction

In the first article 'Saddling HTML Viewer Control' I showed you the way to create the HTML viewer control in eVB using Platform SDK API calls. We managed to show simple html in the control and were able to implement some of the functionality of the HTML Viewer Control such as selecting, copying, text zooming and scrolling. In this article I'll show you that we are able to implement the fully functional HTML viewer control that handles 'links', 'html form' submission, pictures and some more stuff, with the help of the MessageCE control I created.

Background

Let's start from some background on how the HTML viewer control handles links and pictures accordingly to the Windows CE Platform SDK documentation that comes with eMbedded Tools.
If the user taps on a link or submits a form, the HTML viewer control sends the NM_HOTSPOT notification message to its parent, which includes the data structure (NM_HTMLVIEW) with the information about the link reference or the data that was submitted. In the case there is a picture in the html loaded into the control, it will send NM_INLINE_IMAGE notification message with the same data structure, but with the name of the picture file. In the response on this message the Parent is supposed to load this file into the memory and send the DTM_SETIMAGE message with the pointer to the memory of the loaded picture... So much for the simple process of showing the picture, right? Well, worry no more. The subclassing control MessageCE will handle that impossible for eVB situation for you.

So what is this subclassing control anyway? It's a COM component that will hook into the messages of the forms and controls and will notify your eVB application of those messages. I specifically designed the MessageCE control to handle the subclassing and processing of the HTML Viewer control messages.

Implementation

We are going to start from the eVB project we created last time for first article. You will need to download the MessageCE component from http://intelprog.com/prod02.htm and register it on your device using Control Manager.

We'll start from adding some html lines to the HTML Viewer control for showing links and html form.

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