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Internal/screen character mapping: Supressed warnings for re-map and added documentation.
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@ -318,6 +318,58 @@ chip registers.
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</descrip><p>
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</descrip><p>
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<sect1>Character mapping<p>
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The Atari has two representations for characters:
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<enum>
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<item> ATASCII is character mapping which is similar to ASCII and used
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by the CIO system of the OS. This is the default mapping of cc65 when
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producing code for the atari target.
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<item> The internal/screen mapping represents the real value of the
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screen ram when showing a character.
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</enum>
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For direct memory access (simplicity and speed) enabling the internal
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mapping can be useful. This can be achieved by including the
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"<tt/atari_screen_charmap.h/" header.
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A word of caution: Since the <tt/0x00/ character has to be mapped in an
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incompatible way to the C-standard, the usage of string functions in
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conjunction with internal character mapped strings delivers unexpected
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results regarding the string length. The end of strings are detected where
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you may not expect them (to early or (much) to late). Internal mapped
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strings typically support the "<tt/mem...()/" functions.
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<em>For assembler sources the macro "<tt/scrcode/" from the "<tt/atari.mac/"
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package delivers the same feature.</em>
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You can switch back to the ATASCII mapping by including
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"<tt/atari_atascii_charmap.h/".
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A final note: Since cc65 has currently some difficulties with string merging
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under different mappings, defining remapped strings works only flawlessly
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with static array initialization:
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<verb>
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#include <atari\_screen\_charmap.h>
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char pcScreenMappingString[] = "Hello Atari!";
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#include <atari_atascii_charmap.h>
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char pcAtasciiMappingString[] = "Hello Atari!";
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</verb>
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delivers correct results, while
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<verb>
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#include <atari_screen_charmap.h>
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char* pcScreenMappingString = "Hello Atari!";
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#include <atari_atascii_charmap.h>
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char* pcAtasciiMappingString = "Hello Atari!";
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</verb>
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does not.
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<sect>Loadable drivers<p>
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<sect>Loadable drivers<p>
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@ -30,7 +30,10 @@
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/* No include guard here! Multiple use in one file may be intentional. */
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/* No include guard here! Multiple use in one file may be intentional. */
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#pragma warn (remap-zero, push, off)
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#pragma charmap (0x00, 0x40)
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#pragma charmap (0x00, 0x40)
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#pragma warn (remap-zero, pop)
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#pragma charmap (0x01, 0x41)
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#pragma charmap (0x01, 0x41)
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#pragma charmap (0x02, 0x42)
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#pragma charmap (0x02, 0x42)
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#pragma charmap (0x03, 0x43)
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#pragma charmap (0x03, 0x43)
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@ -64,7 +67,10 @@
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#pragma charmap (0x1E, 0x5E)
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#pragma charmap (0x1E, 0x5E)
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#pragma charmap (0x1F, 0x5F)
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#pragma charmap (0x1F, 0x5F)
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#pragma charmap (0x20, 0x00)
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#pragma warn (remap-zero, push, off)
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#pragma charmap (0x20, 0x00)
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#pragma warn (remap-zero, pop)
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#pragma charmap (0x21, 0x01)
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#pragma charmap (0x21, 0x01)
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#pragma charmap (0x22, 0x02)
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#pragma charmap (0x22, 0x02)
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#pragma charmap (0x23, 0x03)
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#pragma charmap (0x23, 0x03)
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