NewCGI package source Useful Components for CGI applications. Do you need to generate dynamic form elements in Delphi? Do you want to include...
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generate dynamic document CGI form data cgi form transformer Delphi Form Editor generate form generate eTDS form generate eTCS form

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Useful Components for CGI applications Gabriel Corneanu Description This is a package for developing CGI applications using Delphi (C++ Builder). One big difference (I would call it advantage) between these components and other packages is that they are used in extension to the standard Borland components for CGI applications. Do you need to generate form elements in Delphi? Do you want to include live images in your pages? Try this! There are some distinct groups of components, described in this document. Custom producers (FLV Converter) This group has one base component, HTMLProducer. It is a direct descendant of PageProducer, with some enhancements. For every custom tag (AMR to MP3 Converter) found in the HTML source, it tries to find one producer that handles the tag. This means the programmer doesn’t have to write code for OnHTMLTag event. The actual producers are all descendents of one ancestor, HTMLBase (abstract), which is also a CustomProducer. They are linked to the HTMLProducer and to one custom tag (by name). The special property editor provided helps you to choose a custom tag at design time. At run time, the HTML producer will replace the custom tag with the content of the first producer registered for that tag. The common properties are: HTMLProducer: is the link to the parent HTMLProducer. HTMLCustomTag: the name of the custom tag to handle. HTMLCustomParams: extra parameters for the generated tag (only for HTML forms components) The producers are: HTMLStatic: it is a simple producer, which includes a text directly into the HTML result. There is one property, HTMLValue (string), which represents the result. HTMLHidden: it is a producer that generates a hidden field, to be included into a form. The properties are HTMLName and HTMLValue, which define the HTML name and value for the hidden field. HTMLCombo: is a producer that generates a SELECT field for a HTML form (the name reflects the Delphi equivalent). It generates options from a dataset. Special properties: Dataset: the dataset to read from. If it is not active, it will try to open it at runtime. HTMLValueFields, HTMLVisibleFields: expression for generating the value of HTML Option tag, respectively the text of the tag. See HTMLFields for details. HTMLSelection: string for determining the initial selection (if set). OneEmpty: generates one empty option (at beginning). OnGetChecked: event for better control of the initial selection. HTMLDBField: a simple producer like HTMLStatic, but it generates the result from Dataset and Field properties. It also wraps the result with a font tag, with parameters from the HTMLTextAttributes property. HTMLImage: it generates an image reference in the document. Here it is only a short description; please see Images for details. HTMLName, HTMLValue: the same as above. They are rarely used with images in HTML. HTMLHeight, HTMLWidth: size of the image. If 0, they are not generated in the output. OnGetImageAction: the event for delivering the image. It is a standard THTTPMethodEvent. You can use the parameters to get the context, and return the right image. Dataset: the dataset to link to. If set, it is possible to use InternalHandling (see Images). HTMLImageType: specify the generated tag; iImage (default) means the result will be IMG tag, and iInputImage means the result will be INPUT tag with IMAGE type (to be used in HTML forms). See the generated HTML. HTMLImageTable: specify the table in the database containing the image (see Images). HTMLKeyFields: fields used to generate parameters for image source. Usually it is a key identifying a record in the above table. See the generated HTML. HTMLImageField: specify the field in the above table containing the image (see Images). UseInternalHandling: the magic property. If you want to get the image from a dataset, and set the right values for the previous 3 properties, then you can try to let the component deliver the image! See Images. HTMLSrcParams: extra parameters you want to add to the image SRC. If using internal handling, it is ignored. Custom Fields The purpose of this group is to help generate HTML form elements to be used with a DataSetTableProducer. This is a very useful component, but unfortunately it was no way (until now) to include (for example) another column for making a selection (check or radio), or an edit field for each row (now even a Image!). And I couldn’t live without it. The solution is to add fake fields into the dataset and let them generate the right HTML! You can enjoy the editor provided with Delphi, and preview the result (not applicable to Images)! So open the fields editor for a table and click new field. Choose a HTML... field, and add a column to the TableProducer, linked to this field. Warning: none of the classic (inherited) properties has effect on these fields. They are calculated fields. Don’t use them for other purposes (like normal editing). Most of the fields have 2 base properties: HTMLNameFields: Fields expression for generating the name of the HTML tag.HTMLValueFields: Fields expression for generating the value of the HTML tag. For HTMLMemo it is the text of the tag; for HTMLText it is the result text. Field list: HTMLCheckBoxField: generates a HTML check element. It has some extra properties: HTMLCheckField: Fields property that dictates the checked status. Must evaluate to boolean. OnGetHTMLChecked: event for more control over the checked status. It is called after evaluating the previous property. HTMLRadioFields: generates a HTML radio element. It has the same properties as the CheckBoxField. It usually has a fixed expression as HTMLNameFields, to act as one group. Of course, it is your decision. HTMLEditField: generates a HTML edit element (type text). You can specify HTMLMaxChar and HTMLSize properties. HTMLMemoFieds: generates a HTML memo (textarea tag). It also has some specific properties: HTMLLines, HTMLSize, HTMLWrapKind. They are directly reflected in the HTML result. HTMLText: generates a text (like HTMLDbField). The purpose is to wrap an existing field with some FONT properties, witch are not available through the columns of the TableProducer. HTMLImageField: generates an image reference in the HTML document. Its behaviour is similar to the HTMLImage component, but it is intended to show the image contained into one database field (see the samples) in the context of a TableProducer. The difference is that you can use other fields for generating name and value (HTMLNameFields, HTMLValueFields). HTMLMultiPage A single component designed to help present the content of a dataset (possible search results) in a multi page manner (every page can have a variable number of rows/columns). It is also a custom producer described in the beginning, so you can include it in another page generated by an HTMLProducer. Specific properties and events are: DataSet: the dataset to go through. HTMLCell: any producer that generates HTML. You can use another HTMLProducer, but take care not to use the same as the parent (may cause a loop). HTMLContentBefore, HTMLContentAfter: other producers to include at the beginning (or the end) of the content. HTMLRowsAttributes, HTMLTableAttributes: some attributes for the generated HTML table. NumCols, NumLines: number of columns and lines (rows) of the HTML table. NumLinks: number of links to generate at the bottom of the content. PageNumVar: name of the parameter used for the page number. It is also used as the text of the links. OnGetNumRec: event for getting the number of results. If using a table, you can use RecordCount; for a query, you may need to use another one with something like "select count(*) from ... where ...". OnPreparePage: event for preparing the page content. You can use it for going to the right record in the dataset. OnPrepareCell: event for preparing the cell content. You can take some extra actions here. Note: for every cell, the Next method of the dataset is called. So you don’t have to do it in the OnPrepareCell event. This component is not finalized (it doesn’t mean that the others are prefect, but here it is space for more work). Any ideas/suggestions are welcome. HTMLFields This is a description of the format used by some properties (HTMLValueFields, HTMLVisibleFields, HTMLNameFields...). Usually the parameters for the tags are combinations depending on some logic. The rule is simple: any text surrounded by "%" is considered to be the name of a field and replaced by the value of that field (in the current dataset). You can use any combination, like "N_%ID1%_%ID2%". If no "%" is found, the output is constant. Two "%%" is replaced with one "%". Example: if you have a combo with some persons, you may want to use some id as the value (the key of a table), and as text a combination of first name and last name, like <OPTION value="123">JOHN DOE<OPTION>. For this, you can set HTMLNameFields="%ID%" and HTMLValueFields="%F_Name% %L_Name%". For radio elements: they are grouped by the name, so usually it is a constant, but the value is a key identifying the row. For checkbox elements, usually it is the opposite: the name depends on a key, and the value is a constant like "on" or "true". For HTMLKeyFields, this is not applicable: it expects to find only a list of existing fields. It is intended for internal use (see Images). The same for HTMLImageField; it only wants a name of a field. Images Here I’m trying to describe what’s going on with (live) images. As you know, an image is not part of the HTML document; it is only a tag containing a link to the actual images. Let’s suppose you have images in a database, and want to output them in HTML. You can save the image to a file, and generate a link to it. Outside of a good garbage collection mechanism for deleting old files, this is not very nice. It is the same problem in JSP, or ASP. The Web server environment must provide some help. I didn’t want to use other storage for the files. And I used another solution: to generate a link back to the same CGI application. Of course, the next call should return the actual image, not the default content. If you are carefully, you can do it in Delphi. But I have already built some support for it, so give it a chance. How it works: for every image, it is generated a link to the same CGI, but a different pathinfo. Don’t worry; everything is done internal, and only at runtime. You only have to write code in the OnGetImageAction event. For this, you can use some helper functions (declared in HTMLCommon): procedure SetResponse(Response:TWebResponse; form:TCustomForm);overload; procedure SetResponse(Response:TWebResponse; bmp:TBitmap);overload; procedure SetResponse(Response:TWebResponse; ctrl:TWinControl);overload; procedure SetResponse(Response:TWebResponse; fld:TField);overload; All of them build an image from a form, from a bitmap, from a WinControl or from a Field (it must be a Blob field, and contain a valid image) and give it as response. As you also know, the usual format for HTML images is jpeg, so all the images are sent in jpeg format (this is because Delphi has support for it). But if the field contains a valid GIF image (or a JPEG image), it is left untouched. I am only looking for some header values, so please report any error. Now if you have a simple HTML page, it is ok. But if you have dynamic pages, like the content of a table (with images), this is not enough. You can’t know in the event what image to deliver. The only help is if you use some parameters as part of the request (included in the image source link). If we are sending the key of the row, than we can handle it. This is the idea. It is not that hard, but it requires some work. So I tried to do as much as possible. I think that in 95% you only have to specify the right properties: keys, image table and field (I’m trying to build a query, so I need the field name, table name and the row key). In 50% I can fill some of these automatically: if using a TTable, the HTMLImageTable is automatically filled with the TableName property and the indexes are scanned for a primary key (or a unique key), and assigned to HTMLKeyFields property; if it finds a TGraphicField, the HTMLImageField is also filled (usually they are just blob fields, so you have to fill it). If using a TQuery and you are including the image field in result, it might help to find the table from the Origin property. There are registered property editors for these properties, but usually you shouldn’t include the image field in the dataset used for generating the table (we don’t need the image field at this time); in this case you won’t find the field in the list. To resume: if the HTMLKeyFields are set, the result is something like <IMG SRC="sameCGI/pathinfo?key1=val1&key2=val2...">. The HTMLImageTable and HTMLImageField are used at the next call (if using internal handling). You can specify extra parameters through HTMLSrcParams, but only if not using internal handling. Other things: the link to the CGI is well formed, even if you are inside some other path. Even more, it is a relative link: try /path/Project1.cgi and /path/Project1.cgi/, and look at the HTML source! I hope I didn’t forget any important thing. I think that the samples included are quite useful. Enhacements There are several property editors, and a special catogory for all the specific properties. Right click in the Object Inspector and choose arrange/by category. Known Issues First I must say this is not a problem with my components. I found it while trying to test the demo projects. I don’t know where this is coming from, but in some cases selecting a blob field in a query with some SQL drivers may return a limited size of the blob. I found this storing some images (>32K) in a MySQL table (LONGBLOB field), and then trying to get them with a query, via ODBC driver. I was surprised to see my pictures truncated. This is not happening if using a TTable component. I don’t know if this is normal, nor if it happening with some other SQL links. This can appear when using internal handling for image components, because I use a query to do it. The only way to avoid it is using a TDatabase for the connection and setting the parameter BLOB SIZE=xx, where xx (in Kb) is large enought for any blob in your particular table. The internal handling is using a TQuery. Because it copies the DatabaseName and SessionName from the original dataset, it works only with TDBDataSet descendants; so It needs BDE. There is no internal support for other DB engines (like ADO, IBExpress), but you can still use the OnGetImageAction event, use a custom query (ADOQuery or else) and set UseInternalHandling to false. Future developing depends on the demand (or on my time), but I think that it should be at least ADO support. I have tried the package with MySql, MSSQL. When a table and/or field contain invalid characters in name (like spaces), the SQL is dependent on the server. For local (Paradox) tables, they must be enclosed in double quotes; MSSQL requires the "" characters. Currenly, it only generates quotes in the query; so it won't work with MSSQL. It needs some work here, to generate more appropriate statements. After recompiling the package (not first time!), please close and restart Delphi. There is no way to "unregister fields" in Delphi, so if you open the new field dialog you will get an error. This is because (I had a look at the sources) (Open source media player) Delphi keeps the registered fields in a list (as pointers), and, without removing them, after recompiling the pointers are invalid. Look at RegisterFields procedure. History Version 2.2 Isolated the midcomp unit; you can use it now on Delphi 5 Pro, removing the MIDCOMP define. Version 2.1 Fixed a small bug, and the demo projects Version 2.0 Added internal handling Basic documentation. Version 1.8 Added (live) Image support (both single and field). Added MultiPageProducer. Added property editors. Registered a property category, for easily usage. Version 1.5 Added HTMLProducer and the other custom producers: Static, Hidden, DBField, and Combo. Added HTMLInQuery for MidasProducer. Version 1.0 First functional version. Not published. Contained only basic field components. Gabriel Corneanu Email: gabrielcorneanu@yahoo.com

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