Qt vs Symbian C++
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I have read about the smart installer, it was at beta 2.0. Whether one bundles the Qt libraries with app code or uses the smart installer, eventually the libraries will be installed on the phone memory. The current footprint is around 8 MB, which on phones like the N97, is quite a lot.
I have tried installing the qt_installer.sis ( this is available in the latest beta SDK) and it always installs in the C: drive, not the mass memory.
I think in future iterations of Qt, it is important for the libraries to be able to run on mass memory, the end user should have this choice.
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bq. I think in future iterations of Qt, it is important for the libraries to be able to run on mass memory, the end user should have this choice.
It is not that easy as You say it is. Please correct me if I’m wrong but usually the devices mass memory is some kind of Flash NAND, in witch case every code stored in this memory needs to be copied in to the devices RAM memory. On the other hand the devices C: drive is usually some kind of Flash NOR, witch can store XIP code (eXecute in Place), this cuts the start-up time substantially because there is no need to copy the code in to RAM.
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To be honest, I have no idea about the differences between how code executes on C:\ vs on the mass memory. But there are so many apps, specifically those written in Symbian C++, which install on either memory just as easily.
Qt, on the other hand, currently does not do that. It somehow installs only on the C:\ drive.
I would hope and expect, in the future, that installing Qt apps on either of these memories be possible.
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[quote author="varunnarula" date="1275402178"]I would hope and expect, in the future, that installing Qt apps on either of these memories be possible. [/quote]
You can easily install Qt applications at mass memory. But Qt libraries should be better installed at c:\ (even if they will work at mass memory) because of performance issues.
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I have tried installing the qt_installer.sis which comes with the (beta) Qt SDK and during installation, the option is provided, but I noticed that all the library components installed on the C: drive.
Have you tried installing any Qt application (bundled with the Qt libraries) on the mass memory. Do let me know, this is something I want to try out.
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Have not tried apps bundled with qt libs, but installing at first qt libs (on main memory) and at second qt app (on SD-card) worked well.
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[quote author="kkrzewniak" date="1275206164"]
It is not that easy as You say it is. Please correct me if I’m wrong but usually the devices mass memory is some kind of Flash NAND, in witch case every code stored in this memory needs to be copied in to the devices RAM memory. On the other hand the devices C: drive is usually some kind of Flash NOR, witch can store XIP code (eXecute in Place), this cuts the start-up time substantially because there is no need to copy the code in to RAM.
[/quote]
No, I'm afraid you are wrong. For many years now the C: drive and the Z: drive (which is where the ROM runs from) have been on NAND flash and are copied to RAM before they run. Typically NOR flash is too slow for modern processors and too expensive compared to NAND + more RAM.A good reason not to store the Qt libs in mass memory is because on some devices that might be a removable card and then any apps installed to C: that needed the libs wouldn't work when the card was removed.
The proper solution to this problem is for Nokia to stop creating devices with too little space on C:!
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bq. The proper solution to this problem is for Nokia to stop creating devices with too little space on C:!
That is exactly the problem. 128 MB will just not cut it. At the very least, 256 MB is required. The N900 has some virtual memory, any idea if something similar can be done on Symbian ?
Take the N97 for example, and with Maps, Quickoffice, Qt and browser cache, the memory quickly fills up. With virtual memory, this problem could be solved.
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No, you're confusing RAM and Flash. Symbian does have virtual memory in the form of demand paging and specifically Writable Data Paging in Symbian^3. That will mean more free RAM but it doesn't help with the amount of space on C: (in fact it could make it worse because that data has to be paged out to flash somewhere!).
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[quote author="varunnarula" date="1275576380"]I have tried installing the qt_installer.sis which comes with the (beta) Qt SDK and during installation, the option is provided, but I noticed that all the library components installed on the C: drive.
Have you tried installing any Qt application (bundled with the Qt libraries) on the mass memory. Do let me know, this is something I want to try out.[/quote]
There was an issue with qt_installer.sis and it need to be installed on c: only. It was said to be fixed in the newer versions.
However, apart from this you can install any Qt Application in the mass memory.
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[quote author="varunnarula" date="1276181289"]bq. The proper solution to this problem is for Nokia to stop creating devices with too little space on C:!
That is exactly the problem. 128 MB will just not cut it. At the very least, 256 MB is required. The N900 has some virtual memory, any idea if something similar can be done on Symbian ?
Take the N97 for example, and with Maps, Quickoffice, Qt and browser cache, the memory quickly fills up. With virtual memory, this problem could be solved.
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I do agree N97 has memory issues. But I think most new devices will handle these issues now.
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The qt_installer.sis was from the beta 1 of the Qt SDK released recently. Have yet to try the one from the latest beta, I believe it is 2.0.
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I hope the N97 is the last phone with 128 MB :-)
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[quote author="QtK" date="1276271405"]
There was an issue with qt_installer.sis and it need to be installed on c: only. It was said to be fixed in the newer versions. [/quote]The reason we force Qt on C: is because otherwise applications startup can take several seconds - we're talking 15 seconds for example. That is simply not acceptable for an end user.
Now, the reason it is slow to load, is because of an overzealous security check on Symbian, where they will re-read and calculate a CRC/MD5/checksum of a library loaded by an app too many times (imagine it's re-reading QtGui 4-5 times for an app startup, just to make sure it's not been tampered with). This check only kicks in for libraries installed on mass memory, so if it's on C this doesn't even happen.
So, basically - is it possible to have Qt installed somewhere else than C, yes. Is it recommended, no. And that's why the qt_installer.sis is hardcoded to put it on C.
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[quote author="snowpong" date="1284454969"][quote author="QtK" date="1276271405"]
There was an issue with qt_installer.sis and it need to be installed on c: only. It was said to be fixed in the newer versions. [/quote]The reason we force Qt on C: is because otherwise applications startup can take several seconds - we're talking 15 seconds for example. That is simply not acceptable for an end user.
Now, the reason it is slow to load, is because of an overzealous security check on Symbian, where they will re-read and calculate a CRC/MD5/checksum of a library loaded by an app too many times (imagine it's re-reading QtGui 4-5 times for an app startup, just to make sure it's not been tampered with). This check only kicks in for libraries installed on mass memory, so if it's on C this doesn't even happen.
So, basically - is it possible to have Qt installed somewhere else than C, yes. Is it recommended, no. And that's why the qt_installer.sis is hardcoded to put it on C.[/quote]
Thank you for making it clear.
Does Nokia smart installer do the same. Because at times you have only a few MB left in C: on your device.
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[quote author="QtK" date="1284456470"]
Thank you for making it clear.Does Nokia smart installer do the same. Because at times you have only a few MB left in C: on your device.
[/quote]The Smart Installer will force it onto C as well, and fail gracefully if there is not enough space.
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[quote author="snowpong" date="1284456669"][quote author="QtK" date="1284456470"]
Thank you for making it clear.Does Nokia smart installer do the same. Because at times you have only a few MB left in C: on your device.
[/quote]The Smart Installer will force it onto C as well, and fail gracefully if there is not enough space.
[/quote]
Will this delay in launching be observed in anyway, if an end-user application has some libraries and are not placed in C:. Or this affects only the Qt runtime libraries.
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[quote author="QtK" date="1284457056"]Will this delay in launching be observed in anyway, if an end-user application has some libraries and are not placed in C:. Or this affects only the Qt runtime libraries.
[/quote]Typically no. It's a special case. You'll experience it if:
Your library is big (2-5megs for example)
You have lots of plugins that link back to your library again
So in general, don't worry. If you have a library with your app it's not gonna hit you in most cases.
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[quote author="snowpong" date="1284457553"][quote author="QtK" date="1284457056"]Will this delay in launching be observed in anyway, if an end-user application has some libraries and are not placed in C:. Or this affects only the Qt runtime libraries.
[/quote]Typically no. It's a special case. You'll experience it if:
Your library is big (2-5megs for example)
You have lots of plugins that link back to your library again
So in general, don't worry. If you have a library with your app it's not gonna hit you in most cases.
[/quote]
Thank you for the clarification.
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I read on forum nokia discussion forums that the smart installer is currently useful only for deploying Qt apps to a very few Symbian devices. The reason cited was lack of space on c drive on most of the current devices. Is this true ? I have one project I'am planning to do in Qt. If the above is true I have to revert back to native Symbian api.